Secondary battery, battery pack, electric vehicle, energy storage system, electric power tool, and electronic unit

ABSTRACT

A secondary battery includes: a cathode, an anode, and a nonaqueous electrolytic solution in a package member having a flat surface, in which the nonaqueous electrolytic solution includes a methylene cyclic carbonate represented by an expression (1): 
     
       
         
         
             
             
         
       
         
         
           
             where R1 and R2 each are a hydrogen group, a halogen group, a monovalent hydrocarbon group, a monovalent halogenated hydrocarbon group, an oxygen-containing monovalent hydrocarbon group, or an oxygen-containing monovalent halogenated hydrocarbon group, and R1 and R2 may be bonded to each other.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application claims priority to Japanese Priority PatentApplication JP 2011-193145 filed in the Japan Patent Office on Sep. 5,2011, JP 2011-218316 filed in the Japan Patent Office on Sep. 30, 2011,the entire content of which is hereby incorporated by reference.

BACKGROUND

The present application relates to a secondary battery including acathode, an anode, and a nonaqueous electrolytic solution, and a batterypack, an electric vehicle, a energy storage system, an electric powertool, and an electronic unit each using the secondary battery.

In recent years, various electronic units such as cellular phones andpersonal digital assistants (PDAs) have been widely used, and furthersize and weight reduction and longer life of the electronic units aredesired. Accordingly, as power supplies for the electronic units,batteries, in particular, small and lightweight secondary batteriescapable of obtaining high energy density have been developed. Recently,other various applications of the secondary batteries, as typified bybattery packs removably mounted in electronic units or the like,electric vehicles such as electric cars, energy storage systems such ashome energy servers, and electric power tools such as electric drillshave been studied.

Secondary batteries obtaining battery capacity with use of variouscharge-discharge principles have been proposed, and in particular,lithium secondary batteries with use of lithium as an electrode reactantholds great promise, because the secondary batteries are allowed toobtain higher energy density than lead-acid batteries or nickel-cadmiumbatteries. The lithium secondary batteries include lithium-ion secondarybatteries using insertion and extraction of lithium ions and lithiummetal secondary batteries using deposition and dissolution of lithiummetal.

The secondary battery includes a cathode, an anode, and an electrolyticsolution, and the electrolytic solution includes a nonaqueous solventand an electrolyte salt. As the electrolytic solution functioning as amedium of charge-discharge reaction exerts a large effect on performanceof the secondary battery, various compositions of the electrolyticsolution have been studied.

More specifically, it is proposed to use a cyclic carbonate having acarbon-carbon double bond (a methylene group) to suppress reductivedecomposition reaction of the electrolytic solution (for example, referto Japanese Unexamined Patent Application Publication No. 2000-058122and Japanese Unexamined Patent Application Publication (PublishedJapanese Translation of PCT application) No. 2010-533359). As the cycliccarbonate having a methylene group, 4-methylene-1,3-dioxolane-2-one,4,4-dimethyl-5-methylene-1,3-dioxolane-2-one, or the like is used.

SUMMARY

In recent years, electronic units and the like using secondary batterieshave higher performance and more functions; therefore, a furtherimprovement in battery characteristics of the secondary batteries isdesired.

It is desirable to provide a secondary battery, a battery pack, anelectric vehicle, an energy storage system, an electric power tool, andan electronic unit which each are capable of obtaining good batterycharacteristics.

According to an embodiment of the technology, there is provided asecondary battery including: a cathode, an anode, and a nonaqueouselectrolytic solution in a package member having a flat surface, whereinthe nonaqueous electrolytic solution includes a methylene cycliccarbonate represented by an expression (1):

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygen-containing monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other.

According to an embodiment of the technology, there is provided abattery pack including: a secondary battery; a control sectioncontrolling a usage state of the secondary battery; and a switch sectionswitching the usage state of the secondary battery according to aninstruction from the control section, in which the secondary batteryincludes a cathode, an anode, and a nonaqueous electrolytic solution ina package member having a flat surface, and the nonaqueous electrolyticsolution includes a methylene cyclic carbonate represented by theabove-described expression (1).

According to an embodiment of the technology, there is provided anelectric vehicle including: a secondary battery; a conversion sectionconverting power supplied from the secondary battery into driving force;a drive section driven by the driving force; and a control sectioncontrolling a usage state of the secondary battery, in which thesecondary battery includes a cathode, an anode, and a nonaqueouselectrolytic solution in a package member having a flat surface, and thenonaqueous electrolytic solution includes a methylene cyclic carbonaterepresented by the above-described expression (1).

According to an embodiment of the technology, there is provided anenergy storage system including: a secondary battery; one or two or moreelectrical units receiving power from the secondary battery; and acontrol section controlling power supply from the secondary battery tothe electrical unit, in which the secondary battery includes a cathode,an anode, and a nonaqueous electrolytic solution in a package memberhaving a flat surface, and the nonaqueous electrolytic solution includesa methylene cyclic carbonate represented by the above-describedexpression (1).

According to an embodiment of the technology, there is provided anelectric power tool including: a secondary battery; and a movablesection receiving power from the secondary battery, in which thesecondary battery includes a cathode, an anode, and a nonaqueouselectrolytic solution in a package member having a flat surface, and thenonaqueous electrolytic solution includes a methylene cyclic carbonaterepresented by the above-described expression (1).

According to an embodiment of the technology, there is provided anelectronic unit including a secondary battery as a power supply, thesecondary battery including a cathode, an anode, and a nonaqueouselectrolytic solution in a package member having a flat surface, inwhich the nonaqueous electrolytic solution includes a methylene cycliccarbonate represented by the above-described expression (1).

In the secondary battery of the technology, the nonaqueous electrolyticsolution is included in the package member having a flat surface, andthe nonaqueous electrolytic solution includes the methylene cycliccarbonate represented by the expression (1); therefore, good batterycharacteristics are allowed to be obtained. Moreover, the battery pack,the electric vehicle, the energy storage system, the electric powertool, and the electronic unit each using the secondary battery of thetechnology are allowed to obtain similar effects.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments and,together with the specification, serve to explain the principles of thetechnology.

FIG. 1 is a sectional view illustrating a configuration of a secondarybattery (prismatic type) according to a first embodiment of thetechnology.

FIG. 2 is a sectional view taken along a line II-II of the secondarybattery illustrated in FIG. 1.

FIG. 3 is an exploded perspective view illustrating a configuration ofanother secondary battery (laminate film type) according to the firstembodiment of the technology.

FIG. 4 is a sectional view taken along a line IV-IV of a spirally woundelectrode body illustrated in FIG. 3.

FIG. 5 is a sectional view illustrating a configuration of a secondarybattery (cylindrical type) according to a second embodiment of thetechnology.

FIG. 6 is an enlarged sectional view illustrating a part of a spirallywound electrode body illustrated in FIG. 5.

FIG. 7 is a block diagram illustrating a configuration of an applicationexample (battery pack) of the secondary battery.

FIG. 8 is a block diagram illustrating a configuration of an applicationexample (electric vehicle) of the secondary battery.

FIG. 9 is a block diagram illustrating a configuration of an applicationexample (energy storage system) of the secondary battery.

FIG. 10 is a block diagram illustrating a configuration of anapplication example (electric power tool) of the secondary battery.

DETAILED DESCRIPTION

Preferred embodiments of the technology will be described in detailbelow referring to the accompanying drawings. It is to be noted thatdescription will be given in the following order.

1. Secondary Battery (First Embodiment)

(methylene cyclic carbonate+package member having flat surface)

1-1. Lithium-ion secondary battery (prismatic type)

1-2. Lithium-ion secondary battery (laminate film type)

1-3. Lithium metal secondary battery (prismatic type, laminate filmtype)

2. Secondary Battery (Second Embodiment)

(methylene cyclic carbonate+dicarbonate compound or the like)

2-1. Lithium-ion secondary battery (cylindrical type)

2-2. Lithium-ion secondary battery (prismatic type, laminate film type)

2-3. Lithium metal secondary battery (cylindrical type, prismatic type,laminate film type)

3. Secondary Battery (Third Embodiment)

(methylene cyclic carbonate+halogenated carbonate)

3-1. Lithium-ion secondary battery (cylindrical type)

3-2. Lithium-ion secondary battery (prismatic type, laminate film type)

3-3. Lithium metal secondary battery (cylindrical type, prismatic type,laminate film type)

4. Secondary Battery (Fourth Embodiment)

(Restriction on structure of methylene cyclic carbonate)

4-1. Lithium-ion secondary battery (cylindrical type)

4-2. Lithium-ion secondary battery (prismatic type, laminate film type)

4-3. Lithium metal secondary battery (cylindrical type, prismatic type,laminate film type)

5. Secondary Battery (Fifth Embodiment)

(methylene cyclic carbonate+unsaturated cyclic carbonate+mixture ratio)

5-1. Lithium-ion secondary battery (cylindrical type)

5-2. Lithium-ion secondary battery (prismatic type, laminate film type)

5-3. Lithium metal secondary battery (cylindrical type, prismatic type,laminate film type)

6. Appropriate Adjustment of Composition of Electrolytic Solution 7.Applications of Secondary Batteries

7-1. Battery pack

7-2. Electric vehicle

7-3. Energy storage system

7-4. Electric power tool

1. Secondary Battery First Embodiment

First, a secondary battery according to a first embodiment of thetechnology will be described below.

(1-1. Lithium-Ion Secondary Battery (Prismatic Type))

FIGS. 1 and 2 illustrate a sectional configuration of the secondarybattery, and

FIG. 2 illustrates a section of the secondary battery taken along a lineII-II in FIG. 1.

[Entire Configuration of Secondary Battery]

The secondary battery is a lithium secondary battery (a lithium-ionsecondary battery) capable of obtaining battery capacity by insertionand extraction of lithium (lithium ions) as an electrode reactant.

The secondary battery described here has a so-called prismatic typebattery configuration. The secondary battery is configured by mainlycontaining a battery device 20 in a battery can 11. The battery device20 is formed by laminating a cathode 21 and an anode 22 with a separator23 in between and then winding them, and has a flat shape correspondingto the shape of the battery can 11. The separator 23 is impregnated witha nonaqueous electrolytic solution (hereinafter simply referred to as“electrolytic solution”) which is a liquid electrolyte.

The battery can 11 is a prismatic package member having one or more flatouter surfaces (one or more flat surfaces 11M). The “flat surface” hasan appearance characteristic in which battery swelling due to gasgeneration in the battery is easily noticeable, because the outersurfaces of the package member in a normal state are flat, and is aconcept against a curved surface in which battery swelling is not easilynoticeable. As illustrated in FIG. 2, in the prismatic package member, asectional surface in a longitudinal direction has a rectangular shape ora substantially rectangular shape (including a curve in part), and mayhave not only a rectangular shape but also an oval shape. In otherwords, the prismatic package member is a vessel-shaped member having arectangular closed end or an oval closed end and an opening with arectangular shape or a substantially rectangular (oval) shape formed byconnecting arcs with straight lines. It is to be noted that FIG. 2illustrates the battery can 11 having a rectangular sectional surface.

The battery can 11 is made of, for example, a conductive material suchas iron, aluminum, or an alloy thereof, and may function as an electrodeterminal. In particular, iron which is harder than aluminum ispreferable to suppress swelling of the battery can 11 during charge anddischarge with use of the hardness (resistance to deformation) of thebattery can 11. It is to be noted that, in the case where the batterycan 11 is made of iron, surfaces of the battery can 11 may be platedwith a metal material such as nickel.

Moreover, the battery can 11 has a hollow configuration having an openend and a closed end, and the battery can 11 is sealed by an insulatingplate 12 and a battery cover 13 attached to the open end. The insulatingplate 12 is disposed between the battery device 20 and the battery cover13, and is made of an insulating material such as polypropylene. Thebattery cover 13 is made of, for example, a material similar to that ofthe battery can 11, and may function as an electrode terminal as in thecase of the battery can 11.

A terminal plate 14 which is a cathode terminal is disposed outside thebattery cover 13, and the terminal plate 14 is electrically insulatedfrom the battery cover 13 by an insulating case 16. The insulating case16 is made of an insulating material such as polybutylene terephthalate.A through hole is provided around the center of the battery cover 13,and a cathode pin 15 is inserted into the through hole to beelectrically connected to the terminal plate 14 and to be electricallyinsulated from the battery cover 13 by a gasket 17. The gasket 17 ismade of, for example, an insulating material, and its surface is coatedwith asphalt.

A cleavage valve 18 and an injection hole 19 are disposed around an edgeof the battery cover 13. The cleavage valve 18 is electrically connectedto the battery cover 13, and when an internal pressure in the secondarybattery increases to a certain extent or higher due to an internal shortcircuit or external application of heat, the cleavage valve 18 isseparated from the battery cover 13 to release the internal pressure.The injection hole 19 is filled with a sealing member 19A made of, forexample, a stainless steel ball.

A cathode lead 24 made of a conductive material such as aluminum isattached to an end (for example, an inside end) of the cathode 21, andan anode lead 25 made of a conductive material such as nickel isattached to an end (for example, an outside end) of the anode 22. Thecathode lead 24 is connected to an end of the cathode pin 15 by weldingor the like, and is electrically connected to the terminal plate 14. Theanode lead 25 is connected to the battery can 11 by welding or the like,and is electrically connected to the battery can 11.

[Cathode]

The cathode 21 includes a cathode current collector 21A and a cathodeactive material layer 21B disposed on one surface or both surfaces ofthe cathode current collector 21A. The cathode current collector 21A ismade of a conductive material such as aluminum, nickel, or stainless.

The cathode active material layer 21B includes, as cathode activematerials, one kind or two or more kinds of cathode materials capable ofinserting and extracting lithium ions, and may include any othermaterial such as a cathode binder or a cathode conductor, if necessary.

As the cathode material, a lithium-containing compound is preferable,because high energy density is obtainable. Examples of thelithium-containing compound include a complex oxide including lithiumand a transition metal element as constituent elements, and a phosphatecompound including lithium and a transition metal element as constituentelements. In particular, the lithium-containing compound including oneor two or more kinds selected from the group consisting of cobalt,nickel, manganese, and iron as transition metal elements is preferable,because a higher voltage is obtainable. The complex oxide and thephosphate compound are represented by, for example, Li_(x)M1O₂ andLi_(y)M2PO₄, respectively. In the expression, M1 and M2 each are one ormore kinds of transition metal elements. The values of x and y depend ona charge-discharge state of the battery, and are generally within arange of 0.05≦x≦1.10 and 0.05≦y≦1.10, respectively.

Examples of the complex oxide including lithium and the transition metalelement include Li_(x)CoO₂ Li_(x)NiO₂, and a lithium-nickel-basedcomplex oxide represented by the following expression (30). Examples ofthe phosphate compound including lithium and the transition metalelement include LiFePO₄ and LiFe_(1-u)Mn_(u)PO₄ (u<1), because highbattery capacity and good cycle characteristics are obtainable.

LiNi_(1z)M_(z)O₂  (30)

where M is one or more kinds selected from the group consisting of Co,Mn, Fe, Al, V, Sn, Mg, Ti, Sr, Ca, Zr, Mo, Tc, Ru, Ta, W, Re, Yb, Cu,Zn, Ba, B, Cr, Si, Ga, P, Sb, and Nb, and z is within a range of0.005<z<0.5.

In addition to the above-described materials, examples of the cathodematerial include oxides, bisulfides, chalcogenides, and conductivepolymers. Examples of the oxides include titanium oxide, vanadium oxide,and manganese dioxide. Examples of the bisulfides include titaniumbisulfide and molybdenum sulfide. Examples of the chalcogenides includeniobium selenide. Examples of the conductive polymers include sulfur,polyaniline, and polythiophene. However, any material other than theabove-described materials may be used as the cathode material.

As the cathode binder, for example, one kind or two or more kinds ofsynthetic rubber or polymer materials are used. Examples of syntheticrubber include styrene butadiene-based rubber, fluorine-based rubber,and ethylene propylene diene. Examples of the polymer materials includepolyvinylidene fluoride and polyimide.

As the cathode conductor, for example, one kind or two or more kinds ofcarbon materials are used. Examples of the cathode materials includegraphite, carbon black, acetylene black, and ketjen black. It is to benoted that the cathode conductor may be a metal material, a conductivepolymer, or the like, as long as the metal material, the conductivepolymer, or the like is a material having electrical conductivity.

[Anode]

The anode 22 includes an anode current collector 22A and an anode activematerial layer 22B disposed on one surface or both surfaces of the anodecurrent collector 22A.

The anode current collector 22A is made of a conductive material such ascopper, nickel, or stainless. The surfaces of the anode currentcollector 22A are preferably roughened, because adhesion of the anodeactive material layer 22B to the anode current collector 22A is improvedby a so-called anchor effect. In this case, the surfaces of the anodecurrent collector 22A may be roughened at least in a region facing theanode active material layer 22B. Examples of a roughening method includea method of forming microparticles by electrolytic treatment. Theelectrolytic treatment is a method of forming microparticles on thesurfaces of the anode current collector 22A in an electrolytic bath byan electrolytic method to form roughened surfaces. Copper foil formed bythe electrolytic treatment is generally called electrolytic copper foil.

The anode active material layer 22B includes, as anode active materials,one kind or two or more kinds of anode materials capable of insertingand extracting lithium ions, and may include any other material such asan anode binder or an anode conductor, if necessary. It is to be notedthat details of the anode binder and the anode conductor are, forexample, similar to those of the cathode binder and the cathodeconductor, respectively. In the anode active material layer 22B, thechargeable capacity of the anode material is larger than the dischargecapacity of the cathode 21 to prevent unintended deposition of lithiummetal during charge and discharge.

Examples of the anode material include carbon materials, becausevariations in crystal structure during insertion and extraction oflithium ions are very small, and high energy density and good cyclecharacteristics are obtainable accordingly. Moreover, it is because thecarbon materials function as anode conductors. Examples of the carbonmaterials include graphitizable carbon, non-graphitizable carbon havingthe (002) plane with a surface separation of 0.37 nm or over, andgraphite having the (002) plane with a surface separation of 0.34 nm orless. More specific examples of the carbon materials include pyrolyticcarbons, cokes, glass-like carbon fibers, an organic polymer compoundfired body, activated carbon, and carbon blacks. Cokes include pitchcoke, needle coke, and petroleum coke. The organic polymer compoundfired body is formed by firing (carbonizing) a polymer compound such asa phenolic resin or a furan resin at an appropriate temperature. Inaddition, as the carbon material, low-crystalline carbon or amorphouscarbon subjected to heat treatment at approximately 1000° C. or less maybe used. It is to be noted that the carbon material may have any of afibrous shape, a spherical shape, a granular shape, and a scale-likeshape.

In addition, examples of the anode material may include metal oxides andpolymer compounds. Examples of metal oxides include iron oxide,ruthenium oxide, and molybdenum oxide. Examples of the polymer compoundsinclude polyacetylene, polyaniline, and polypyrrole. However, anymaterial other than the above-described materials may be used as theanode material.

The anode active material layer 22B is formed by, for example, a coatingmethod, a vapor-phase method, a liquid-phase method, a spraying method,a firing method (a sintering method), or a combination of two or morekinds of the methods. In the coating method, for example, a particulateanode active material is mixed with the anode binder or the like to forma mixture, and the mixture is dispersed in a solvent such as an organicsolvent, and then coating with the mixture is performed. Examples of thevapor-phase method include a physical deposition method and a chemicaldeposition method. More specific examples of the vapor-phase methodinclude a vacuum deposition method, a sputtering method, an ion platingmethod, a laser ablation method, a thermal chemical vapor depositionmethod, a chemical vapor deposition (CVD) method, and a plasma chemicalvapor deposition method. Examples of the liquid-phase method include anelectrolytic plating method, and an electroless plating method. In thespray method, the anode active material in a molten state or asemi-molten state is sprayed. In the firing method, for example, aftercoating is performed by the coating method, the mixture is heated at ahigher temperature than the melting point of the anode binder or thelike. As the firing method, a known technique may be used. Examples ofthe firing method include an atmosphere firing method, a reaction firingmethod, and a hot press firing method.

[Separator]

The separator 23 isolates between the cathode 21 and the anode 22 toallow lithium ions to pass therethrough while preventing a short circuitof a current due to contact between the cathode 21 and the anode 22. Theseparator 23 is configured of, for example, a porous film of a syntheticresin or ceramic, and may be configured of a laminate film formed bylaminating two or more kinds of porous films. Examples of the syntheticresin include polytetrafluoroethylene, polypropylene, and polyethylene.

In particular, for example, the separator 23 may include a base layermade of the above-described porous film and a polymer compound layerdisposed on one surface or both surfaces of the base layer, becauseadhesion of the separator 23 to the cathode 21 and the anode 22 isimproved, thereby suppressing distortion of the battery device 20 whichis a spirally wound body. Thus, decomposition reaction of theelectrolytic solution is suppressed, and leakage of the electrolyticsolution with which the base layer is impregnated is suppressed;therefore, if charge and discharge are repeated, resistance of thesecondary battery is less likely to increase, and battery swelling issuppressed.

The polymer compound layer includes, for example, a polymer materialsuch as polyvinylidene fluoride, because the polymer material is good inphysical strength and is electrochemically stable. However, the polymermaterial may be any polymer material other than polyvinylidene fluoride.For example, the polymer compound layer is formed by preparing asolution in which the polymer material is dissolved, and then coating asurface of the base layer with the solution, and drying the base layer.It is to be noted that the base layer may be immersed in the solution,and then dried.

[Electrolytic Solution]

The electrolytic solution with which the separator 23 is impregnatedincludes a methylene cyclic carbonate represented by the followingexpression (1). However, the electrolytic solution may include othermaterials such as a nonaqueous solvent and an electrolyte salt.

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygen-containing monovalent hydrocarbon group or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other.

The methylene cyclic carbonate is a carbonate compound having amethylene group as an unsaturated carbon bond (a carbon-carbon doublebond) outside a ring structure (a five-membered ring). As a firm coatingis formed on a surface of the anode 22 mainly during initial charge, theelectrolytic solution includes the methylene cyclic carbonate tosuppress decomposition reaction of the electrolytic solution caused byreactivity of the anode 22. Therefore, high battery capacity isobtainable even during initial charge and discharge, thereby improvinginitial charge-discharge characteristics. Moreover, gas generationcaused by decomposition reaction of the electrolytic solution issuppressed not only during initial charge and discharge but also duringstorage of the secondary battery at high temperature, thereby improvingswelling characteristics. In particular, in the prismatic secondarybattery in which battery swelling is easily noticeable by the flatsurface 11M of the battery can 11, battery swelling is effectivelysuppressed.

Kinds of R1 and R2 are not specifically limited, as long as, asdescribed above, they each are the hydrogen group, the halogen group,the monovalent hydrocarbon group, the monovalent halogenated hydrocarbongroup, the oxygencontaining monovalent hydrocarbon group, or theoxygen-containing monovalent halogenated hydrocarbon group, because themethylene cyclic carbonate has a carbonate ring structure (afive-membered ring) and a unsaturated carbon bond (a methylene group),thereby allowing the above-described advantages to be obtained withoutrelying on the kinds of R1 and R2. It is to be noted that the kinds ofR1 and R2 may be the same as or different from each other. The ringstructure may be formed by bonding R1 and R2 to each other.

Here, the “hydrocarbon group” is a generic name of a group includingcarbon and hydrogen, and may have a straight-chain structure or abranched structure. Moreover, the “halogenated hydrocarbon group” is agroup obtained by halogenating the above-described hydrocarbon group,that is, a group in which one or more of hydrogen groups in thehydrocarbon group is substituted with a halogen group. As the halogengroup, for example, one kind or two or more kinds selected from thegroup consisting of a fluorine group (—F), a chlorine group (—Cl), abromine group (—Br), and an iodine group (—I) are used, and inparticular, the fluorine group is preferable, because a coating causedby the methylene cyclic carbonate is easily formed.

In R1 and R2, specific examples of the halogen group are similar tothose in the case where the “halogenated hydrocarbon group” is describedabove. Specific examples of the monovalent hydrocarbon group include analkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an arylgroup having 6 to 18 carbon atoms, and a cycloalkyl group having 3 to 18carbon atoms. Moreover, the monovalent halogenated hydrocarbon group isa group obtained by substituting one or more of hydrogen groups in theabove-described alkyl group or the like with a halogen group. The alkylgroup, the alkenyl group, or the alkynyl group may have a straight-chainstructure, or a branched structure having one or two or more sidechains, because the above-described advantages are obtainable whilesecuring solubility, compatibility, and the like of the methylene cycliccarbonate. However, R1 and R2 each may be a group other than theabove-described groups.

More specifically, examples of the alkyl group include a methyl group(—CH₃), an ethyl group (—C₂H₅), and a propyl group (—C₃H₇). Examples ofthe alkenyl group include a vinyl group (—C₂H₃) and an allyl group(—C₃H₅). Examples of the alkynyl group include an ethynyl group (—C₂H₁).Examples of the aryl group include a phenyl group and a naphthyl group.Examples of the cycloalkyl group include a cyclopropyl group, acyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptylgroup, and a cyclooctyl group. Examples of a group obtained byhalogenating the alkyl group or the like include a trifluoromethyl group(—CF₃) and a pentafluoroethyl group (—C₂F₅). The above-described groupsare just examples, and any other group may be used.

The “oxygen-containing hydrocarbon group” is a group including carbon,hydrogen, and oxygen. The “oxygen-containing halogenated hydrocarbongroup” is a group obtained by substituting one or more of hydrogengroups in the above-described oxygen-containing hydrocarbon group with ahalogen group, and the kind of the halogen group is as described above.

Examples of the oxygen-containing monovalent hydrocarbon group includean alkoxy group having 1 to 12 carbon atoms. Moreover, for example, theoxygen-containing monovalent halogenated hydrocarbon group is a groupobtained by substituting one or more of hydrogen groups in theabove-described alkoxy group or the like with a halogen group, becausethe above-described advantages are obtainable while securing solubility,compatibility, and the like of the methylene cyclic carbonate.

Specific examples of the alkoxy group include a methoxy group (—OCH₃)and an ethoxy group (—OC₂H₅). Examples of a group obtained byhalogenating the alkoxy group or the like include a trifluoromethoxygroup (—OCF₃) and a pentafluoroethoxy group (—OC₂F₅).

It is to be noted that R1 and R2 each may be a derivative of any one ofthe above-described groups. The derivative is a group obtained byintroducing one or two or more substituent groups into any of theabove-described groups, and the kind of the substituent group isarbitrarily selected. A derivative may be used for R11 and later groupswhich will be described later in a similar manner.

Specific examples of the methylene cyclic carbonate are represented bythe following expressions (1-1) to (1-31). It is to be noted that R1 andR2 may be bonded to each other; therefore, as illustrated in theexpression (1-31), R1 and R2 bonded to each other may be methylenegroups (—CH₂—).

The content of the methylene cyclic carbonate in the electrolyticsolution is not specifically limited, but is preferably within a rangeof 0.01 wt % to 10 wt % both inclusive, and more preferably within arange of 0.1 wt % to 5 wt % both inclusive, because a higher effect isobtainable.

The nonaqueous solvent includes one kind or two or more kinds of organicsolvents (except for the above-described methylene cyclic carbonate).

Examples of the organic solvent include ethylene carbonate, propylenecarbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate,ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone,γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran,2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane,4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, methyl acetate, ethylacetate, methyl propionate, ethyl propionate, methyl butyrate, methylisobutyrate, methyl trimethylacetate, ethyl trimethylacetate,acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile,3-methoxypropionitrile, N,N-dimethylformamide, Nmethylpyrrolidinone,N-methyloxazolidinone, N,N′-dimethylimidazolidinone, nitromethane,nitroethane, sulfolane, trimethyl phosphate, and dimethyl sulfoxide,because good battery capacity, good cycle characteristics, good storagecharacteristics, and the like are obtainable.

In particular, one or more kinds selected from the group consisting ofethylene carbonate and propylene carbonate which are cyclic carbonates,and dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonatewhich are chain carbonates are preferable, because higher batterycapacity, better cycle characteristics, better storage characteristics,and the like are obtainable. In this case, a combination of ahigh-viscosity (high-permittivity) solvent (for example, relativepermittivity ε≧30) such as ethylene carbonate or propylene carbonate anda low-viscosity solvent (for example, viscosity≦1 mPa·s) such asdimethyl carbonate, ethyl methyl carbonate or diethyl carbonate is morepreferable, because the dissociation property of the electrolyte saltand ion mobility are improved.

In particular, the nonaqueous solvent preferably includes one kind ortwo or more kinds selected from unsaturated cyclic carbonatesrepresented by the following expressions (2) and (3), because a coatingis formed on the surface of the anode 22 mainly during charge anddischarge, thereby suppressing decomposition reaction of theelectrolytic solution. The unsaturated cyclic carbonate is a cycliccarbonate having one or two or more unsaturated carbon bonds(carbon-carbon double bonds). The kinds of R11 and R12 may be the sameas or different from each other. The kinds of R13 to R16 may be the sameas or different from one another, or two or more of R13 to R16 may bethe same as one another. The content of the unsaturated cyclic carbonatein the nonaqueous solvent is not specifically limited, but is, forexample, within a range of 0.01 wt % to 10 wt % both inclusive. It is tobe noted that specific examples of the unsaturated cyclic carbonate mayinclude not only compounds which will be described below, but also othercompounds.

where R11 and R12 each are a hydrogen group or an alkyl group.

where R13 to R16 each are a hydrogen group, an alkyl group, a vinylgroup, or an allyl group, and one or more of R13 to R16 is a vinyl groupor an allyl group.

The unsaturated cyclic carbonate represented by the expression (2) is avinylene carbonate-based compound. Examples of the vinylenecarbonate-based compound include vinylene carbonate (1,3-dioxol-2-one),methyl vinylene carbonate (4-methyl-1,3-dioxol-2-one), ethyl vinylenecarbonate (4-ethyl-1,3-dioxol-2-one), 4,5-dimethyl-1,3-dioxol-2-one,4,5-diethyl-1,3-dioxol-2-one, 4-fluoro-1,3-dioxol-2-one, and4-trifluoromethyl-1,3-dioxol-2-one. In particular, vinylene carbonate ispreferable, because vinylene carbonate is easily available, and a higheffect is obtainable.

The unsaturated cyclic carbonate represented by the expression (3) is avinyl ethylene carbonate-based compound. Examples of the vinyl ethylenecarbonate-based compound include vinyl ethylene carbonate,4-methyl-4-vinyl-1,3-dioxolane-2-one,4-ethyl-4-vinyl-1,3-dioxolane-2-one,4-n-propyl-4-vinyl-1,3-dioxolane-2-one,5-methyl-4-vinyl-1,3-dioxolane-2-one, 4,4-divinyl-1,3-dioxolane-2-one,and 4,5-divinyl-1,3-dioxolane-2-one. In particular, vinyl ethylenecarbonate is preferable, because vinyl ethylene carbonate is easilyavailable, and a high effect is obtainable. All of R13 to R16 may bevinyl groups or allyl groups, or vinyl groups and allyl groups may bemixed in R13 to R16.

It is to be noted that the unsaturated cyclic carbonate may be catecholcarbonate having a benzene ring in addition to the compounds representedby the expressions (2) and (3).

Moreover, the nonaqueous solvent preferably includes one kind or two ormore kinds selected from halogenated carbonates represented by thefollowing expressions (4) and (5), because a coating is formed on thesurface of the anode 22 mainly during charge and discharge, therebysuppressing decomposition reaction of the electrolytic solution. Thehalogenated carbonate represented by the expression (4) is a cycliccarbonate (a halogenated cyclic carbonate) having one or two or morehalogen atoms as constituent elements. On the other hand, thehalogenated carbonate represented by the expression (5) is a chaincarbonate (halogenated chain carbonate) having one or two or morehalogen atoms as constituent elements. The kinds of R17 to R20 may bethe same as or different from one another, and two or more of R17 to R20may be the same as one another. The same applies to R21 to R26. Thecontent of the halogenated carbonate in the nonaqueous solvent is notspecifically limited, but is, for example, within a range of 0.01 wt %to 50 wt % both inclusive. However, specific examples of the halogenatedcarbonate include not only compounds which will be described below butalso other compounds.

where R17 to R20 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R17 to R20 is a halogen group or a monovalenthalogenated hydrocarbon group.

where R21 to R26 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R21 to R26 is a halogen group or a monovalenthalogenated hydrocarbon group.

The kind of halogen is not specifically limited; however, in particular,fluorine (F), chlorine (Cl) or bromine (Br) is preferable, and fluorineis more preferable, because a higher effect than that of other halogensis obtainable. The number of halogen atoms is more preferably 2 than 1,and may be 3 or more, because a capability of forming a coating isimproved, and a firmer and stabler coating is formed, thereby furthersuppressing decomposition reaction of the electrolytic solution.

The kinds of R17 to 26 are not specifically limited, as long as theyeach are a hydrogen group, a halogen group, a monovalent hydrocarbongroup, or a monovalent halogenated hydrocarbon group, as describedabove. However, as a condition, one or more of R17 to R20 is a halogengroup or a monovalent halogenated hydrocarbon group. The same applies toR21 to R26. Specific examples of the halogen group are similar to theabove-described kinds of halogen. Specific examples of the monovalenthydrocarbon group include an alkyl group having 1 to 12 carbon atoms,and specific examples of the monovalent halogenated hydrocarbon groupinclude a group in which one or more of hydrogen groups in theabove-described alkyl group or the like is substituted with a halogengroup. However, the alkyl group may have a straight-chain structure, ora branched structure having one or two or more side chains.

Examples of the halogenated cyclic carbonate include compoundsrepresented by expressions (4-1) to (4-21), and also include a geometricisomer. In particular, 4-fluoro-1,3-dioxolane-2-one represented by theexpression (4-1) and 4,5-difluoro-1,3-dioxolane-2-one represented by theexpression (4-3) are preferable, and the latter carbonate is morepreferable. Moreover, as 4,5-difluoro-1,3-dioxolane-2-one, a transisomeris more preferable than a cis-isomer, because it is easily available,and a high effect is obtainable. On the other hand, examples of thehalogenated chain carbonate include fluoromethyl methyl carbonate,bis(fluoromethyl)carbonate, and difluoromethyl methyl carbonate.

The electrolyte salt includes, for example, one kind or two or morekinds of salts such as lithium salt. However, the electrolyte salt mayinclude, for example, any salt other than lithium salt (for example, alight-metal salt other than lithium salt).

Examples of the lithium salt include lithium hexafluorophosphate(LiPF₆), lithium tetrafluoroborate (LiBF₄), lithium perchlorate(LiClO₄), lithium hexafluoroarsenate (LiAsF₆), lithium tetraphenylborate (LiB(C₆H₅)₄), lithium methanesulfonate (LiCH₃SO₃).trifluoromethane sulfonic lithium (LiCF₃SO₃), lithiumtetrachloroaluminate (LiAlCl₄), lithium silicate hexafluoride (Li₂SiF₆),lithium chloride (LiCl), and lithium bromide (LiBr), because goodbattery capacity, good cycle characteristics, good storagecharacteristics, and the like are obtainable. However, specific examplesof lithium salt may include not only the above-described compound butalso other compounds.

In particular, one or more kinds selected from the group consisting oflithium hexafluorophosphate, lithium tetrafluoroborate, lithiumperchlorate, and lithium hexafluoroarsenate are preferable, and lithiumhexafluorophosphate is more preferable, because internal resistance isreduced; therefore, a higher effect is obtainable.

In particular, the electrolyte salt preferably includes one kind or twoor more kinds selected from compounds represented by the followingexpressions (6) to (8), because higher characteristics are obtainable.It is to be noted that the kinds of R31 and R33 may be the same as ordifferent from each other. The same applies to R41 to R43, and R51 andR52. However, specific examples of the compounds represented by theexpressions (6) to (8) may include not only compounds which will bedescribed below but also other compounds.

where X31 is a Group 1 element or a Group 2 element in the long form ofthe periodic table of the elements, or aluminum, M31 is a transitionmetal element, or a Group 13 element, a Group 14 element, or a Group 15element in the long form of the periodic table of the elements, R31 is ahalogen group, Y31 is —C(O═)—R32-C(═O)—, —C(O═)—CR33₂-, or—C(═O)—C(═O)—, in which R32 is an alkylene group, a halogenated alkylenegroup, an arylene group or a halogenated arylene group, R33 is an alkylgroup, a halogenated alkyl group, an aryl group or a halogenated arylgroup, a3 is an integer of 1 to 4, b3 is an integer of 0, 2 or 4, andc3, d3, m3, and n3 each are an integer of 1 to 3.

where X41 is a Group 1 element or a Group 2 element in the long form ofthe periodic table of the elements, M41 is a transition metal element,or a Group 13 element, a Group 14 element, or a Group 15 element in thelong form of the periodic table of the elements, Y41 is—C(═O)—(CR41₂)_(b4)-C(═O)—, —R43₂C—(CR42₂)_(c4)-C(═O)—,—R43₂C—(CR42₂)_(c4)-CR43₂-, —R43₂C—(CR42₂)_(c4)-S(═O)₂—,—S(═O)₂—(CR42₂)_(d4)-S(═O)₂—, or —C(═O)—(CR42₂)_(d4)-S(═O)₂—, in whichR41 and R43 each are a hydrogen group, an alkyl group, a halogen group,or a halogenated alkyl group, and one or both of them are a halogengroup or a halogenated alkyl group, R42 is a hydrogen group, an alkylgroup, a halogen group, or a halogenated alkyl group, and a4, e4, and n4each are an integer of 1 or 2, b4 and d4 each are an integer of 1 to 4,c4 is an integer of 0 to 4, and f4 and m4 each are an integer of 1 to 3.

where X51 is a Group 1 element or a Group 2 element in the long form ofthe periodic table of the elements, M51 is a transition metal element,or a Group 13 element, a Group 14 element, or a Group 15 element in thelong form of the periodic table of the elements, Rf is a fluorinatedalkyl group having 1 to 10 carbon atoms or a fluorinated aryl grouphaving 1 to 10 carbon atoms, Y51 is —C(═O)—(CR51₂)_(d5)-C(═O)—,—R52₂C—(CR51₂)_(d5)-C(═O)—, —R52₂C—(CR51₂)_(d5)-CR52₂—,—R52₂C—(CR51₂)_(d5)-S(═O)₂—, —S(═O)₂—(CR51₂)_(e5)-S(═O)₂—, or—C(═O)—(CR51₂)_(e5)-S(═O)₂—, in which R51 is a hydrogen group, an alkylgroup, a halogen group or a halogenated alkyl group, R52 is a hydrogengroup, an alkyl group, a halogen group, or a halogenated alkyl group,and one or more of them is a halogen group or a halogenated alkyl group,and a5, f5, and n5 each are an integer of 1 or 2, b5, c5, and e5 eachare an integer of 1 to 4, d5 is an integer of 0 to 4, and g5 and m5 eachare an integer of 1 to 3.

It is to be noted that Group 1 elements include hydrogen, lithium,sodium, potassium, rubidium, cesium, and francium. Group 2 elementsinclude beryllium, magnesium, calcium, strontium, barium, and radium.Group 13 elements include boron, aluminum, gallium, indium, andthallium. Group 14 elements include carbon, silicon, germanium, tin, andlead. Group 15 elements include nitrogen, phosphorus, arsenic, antimony,and bismuth.

Examples of the compound represented by the expression (6) includecompounds represented by expressions (6-1) to (6-6). Examples of thecompound represented by the expression (7) include compounds representedby expressions (7-1) to (7-8). Examples of the compound represented bythe expression (8) include a compound represented by an expression(8-1).

Moreover, the electrolyte salt preferably includes one kind or two ormore kinds selected from compounds represented by the followingexpressions (9) to (11), because higher characteristics are obtainable.It is to be noted that the values of m and n may be the same as ordifferent from each other. The same applied to p, q, and r. However,specific examples of the compounds represented by the expressions (9) to(11) may include not only compounds which will be described below butalso other compounds.

LiN(C_(m)F_(2m+1)SO₂)(C_(n)F_(2n+1)SO₂)  (9)

where m and n each are an integer of 1 or more.

where R61 is a straight-chain or branched perfluoroalkylene group having2 to 4 carbon atoms.

LiC(C_(p)F_(2p+1)SO₂)(C_(g)F_(2q+1)SO₂)(C_(r)F_(2r+1)SO₂)  (11)

where p, q, and r each are an integer of 1 or more.

The compound represented by the expression (9) is a chain imidecompound, and examples thereof include lithiumbis(trifluoromethane-sulfonyl)imide (LiN(CF₃SO₂)₂), lithiumbis(pentafluoroethanesulfonyl)imide (LiN(C₂F₅SO₂)₂)₅ lithium(trifluoromethanesulfonyl)(pentafluoroethanesulfonyl)imide(LiN(CF₃SO₂)(C₂F₅SO₂)), lithium(trifluoromethanesulfonyl)(heptafluoropropanesulfonyl)imide(LiN(CF₃SO₂)(C₃F₇SO₂)), and lithium(trifluoromethanesulfonyl)(nonafluorobutanesulfonyl)imide(LiN(CF₃SO₂)(C₄F₉SO₂)).

The compound represented by the expression (10) is a cyclic imidecompound, and examples thereof include compounds represented byexpressions (10-1) to (10-4).

The compound represented by the expression (11) is a chain methidecompound, and examples thereof include lithiumtris(trifluoromethanesulfonyl)methide (LiC(CF₃SO₂)₃).

The content of the electrolyte salt is not specifically limited, but ispreferably within a range from 0.3 mol/kg to 3.0 mol/kg both inclusiverelative to the nonaqueous solvent, because high ionic conductivity isobtainable.

[Operation of Secondary Battery]

In the secondary battery, for example, lithium ions extracted from thecathode 21 are inserted into the anode 22 through the electrolyticsolution during charge, and lithium ions extracted from the anode 22 areinserted into the cathode 21 through the electrolytic solution duringdischarge.

[Method of Manufacturing Secondary Battery]

The secondary battery is manufactured by, for example, the followingsteps.

First of all, the cathode 21 is formed. First, the cathode activematerial and, if necessary, the cathode binder, the cathode conductor,and the like are mixed to form a cathode mixture. Then, the cathodemixture is dispersed in an organic solvent or the like to formpaste-form cathode mixture slurry. Next, both surfaces of the cathodecurrent collector 21A are coated with the cathode mixture slurry, andthe cathode mixture slurry is dried to form the cathode active materiallayer 21B. Then, the cathode active material layer 21B is compressionmolded by a roller press or the like while applying heat, if necessary.In this case, compression molding may be repeated a plurality of times.

Moreover, the anode 22 is formed by steps similar to the above-describedsteps of forming the cathode 21. An anode mixture is formed by mixingthe anode active material and, if necessary, the anode binder, the anodeconductor, and the like, and the anode mixture is dispersed in anorganic solvent or the like to form paste-form anode mixture slurry.Next, both surfaces of the anode current collector 22A are coated withthe anode mixture slurry, and the anode mixture slurry is dried to formthe anode active material layer 22B. Then, if necessary, the anodeactive material layer 22B is compression molded.

Further, the electrolyte salt is dispersed in the nonaqueous solvent,and then the methylene cyclic carbonate is added to the nonaqueoussolvent to prepare the electrolytic solution.

Next, the battery device 20 is formed. First, the cathode lead 24 andthe anode lead 25 are attached to the cathode current collector 21A andthe anode current collector 22A, respectively, by a welding method orthe like. Then, the cathode 21 and the anode 22 are laminated with theseparator 23 in between, and they are spirally wound in a longitudinaldirection to form a spirally wound body. Finally, the spirally woundbody is molded to have a flat shape.

Finally, the secondary battery is assembled. First, the battery device20 is contained in the battery can 11, and then the insulating plate 12is placed on the battery device 20. Next, the cathode lead 24 and theanode lead 25 are attached to the cathode pin 15 and the battery can 11,respectively, by a welding method or the like. In this case, the batterycover 13 is fixed to an open end of the battery can 11 by a laserwelding method or the like. Finally, the electrolytic solution isinjected into the battery can 11 from the injection hole 19 toimpregnate the separator 23 with the electrolytic solution, and then theinjection hole 19 is sealed with the sealing member 19A.

[Functions and Effects of Secondary Battery]

In the prismatic type secondary battery, the electrolytic solution iscontained in the battery can 11 having the flat surface 11M, and theelectrolytic solution includes the methylene cyclic carbonate. In thiscase, as described above, decomposition reaction of the electrolyticsolution caused by reactivity of the anode 22 is suppressed; therefore,initial charge-discharge characteristics are improved. Moreover, gasgeneration caused by decomposition reaction of the electrolytic solutionnot only during the initial charge and discharge but also while storageof the secondary battery at high temperature is suppressed; therefore,swelling characteristics are also improved. Thus, the initialcharge-discharge characteristics and the swelling characteristics areboth improved; therefore, good battery characteristics are allowed to beobtained.

In particular, when the content of the methylene cyclic carbonate in theelectrolytic solution is within a range of 0.01 wt % to 10 wt % bothinclusive, more specifically within a range of 0.1 wt % to 5 wt % bothinclusive, a higher effect is allowed to be obtained.

(1-2. Lithium-Ion Secondary Battery (Laminate Film Type))

FIGS. 3 and 4 illustrate a sectional configuration of another secondarybattery, and FIG. 4 illustrates a section of the spirally woundelectrode body 30 taken along a line IV-IV in FIG. 3. A description willbe given of constituent components of the secondary battery withreference to the above-described components of the prismatic typesecondary battery as appropriate.

[Entire Configuration of Secondary Battery]

The secondary battery is a lithium-ion secondary battery capable ofobtaining battery capacity by insertion and extraction of lithium ionsas in the case of the prismatic type secondary battery.

The secondary battery described here has a so-called laminate film typebattery configuration. In the secondary battery, mainly a spirally woundelectrode body 30 as the battery device is contained in a package member39, and the spirally wound electrode body 30 is formed by laminating thecathode 33 and the anode 34 with the separator 35 impregnated with theelectrolytic solution in between, and spirally winding them. The cathodelead 31 and the anode lead 32 are attached to the cathode 33 and theanode 34, respectively. An outermost portion of the spirally woundelectrode body 30 is protected with a protective tape 37.

The cathode lead 31 and the anode lead 32 are drawn, for example, fromthe interiors of the package members 39 to outside in the samedirection. The cathode lead 31 is made of, for example, a conductivematerial such as aluminum, and the anode lead 32 are made of, forexample, a conductive material such as copper, nickel, or stainless.These conductive materials each have a sheet shape or a mesh shape.

The package members 39 are film-shaped package members having one ormore flat outer surfaces (one or more flat surfaces 39M), and arelaminate films formed by laminating, for example, a bonding layer, ametal layer, and a surface protection layer in this order. In thelaminate films, for example, edge portions of the bonding layers of twolaminate films are adhered to each other by fusion bonding or anadhesive to allow the bonding layers to face the spirally woundelectrode body 30. The bonding layer is, for example, a film ofpolyethylene or polypropylene. The metal layer is, for example, aluminumfoil. The surface protection layer is, for example, a film of nylon orpolyethylene terephthalate.

In particular, as the package members 39, aluminum laminate films eachformed by laminating a polyethylene film, aluminum foil, and a nylonfilm in this order are preferable. However, the package members 39 maybe laminate films with any other laminate configuration, a polymer filmof polypropylene or the like, or a metal film.

Adhesive films 38 for preventing the entry of outside air are insertedbetween each package member 39 and the cathode lead 31 and between eachpackage member 39 and the anode lead 32. The adhesive films 38 are madeof, for example, a material having adhesion to the cathode lead 31 andthe anode lead 32. Examples of such a material include polyolefin resinssuch as polyethylene, polypropylene, modified polyethylene, and modifiedpolypropylene.

The cathode 33 includes, for example, a cathode current collector 33Aand a cathode active material layer 33B disposed on both surfaces of thecathode current collector 33A. The anode 34 includes, for example, ananode current collector 34A and an anode active material layer 34Bdisposed on both surfaces of the anode current collector 34A. Theconfigurations of the cathode current collector 33A, the cathode activematerial layer 33B, the anode current collector 34A, and the anodeactive material layer 34B are similar to those of the cathode currentcollector 21A, the cathode active material layer 21B, the anode currentcollector 22A, and the anode active material layer 22B, respectively.

The configuration of the separator 35 is similar to that of theseparator 23, and the composition of the electrolytic solution withwhich the separator 35 is impregnated is similar to that in theprismatic type secondary battery.

[Operation of Secondary Battery]

In the secondary battery, for example, lithium ions extracted from thecathode 33 are inserted into the anode 34 through the electrolyte layer36 during charge. On the other hand, for example, lithium ions extractedfrom the anode 34 are inserted into the cathode 33 through theelectrolyte layer 36 during discharge.

[Method of Manufacturing Secondary Battery]

The secondary battery is manufactured by, for example, the followingsteps.

First, the cathode 33 and the anode 34 are formed by steps similar tothe steps of forming the cathode 21 and the anode 22. In this case, thecathode active material layer 33B is formed on both surfaces of thecathode current collector 33A to form the cathode 33, and the anodeactive material layer 34 is formed on both surfaces of the anode currentcollector 34A to form the anode 34. Next, the cathode lead 31 and theanode lead 32 are attached to the cathode current collector 33A and theanode current collector 34A, respectively, by a welding method or thelike. Then, the cathode 33 and the anode 34 are laminated with theseparator 35 in between, and they are spirally wound to form thespirally wound electrode body 30, and then the protective tape 37 isbonded to an outermost part of the spirally wound electrode body 30.Next, the spirally wound electrode body 30 is sandwiched between twofilm-shaped package members 39, and then the electrolytic solution isinjected into the package members 39 to impregnate the separator 35 withthe electrolytic solution. Next, edge portions of the package members 39are adhered to each other by a thermal fusion bonding method or the liketo seal the spirally wound electrode body 30 in the package members 39.In this case, the adhesive films 38 are inserted between the cathodelead 31 and each package member 39 and between the anode lead 32 andeach package member 39.

[Functions and Effects of Secondary Battery]

In the laminate film type secondary battery, the electrolytic solutionis contained in the package members 39 having the flat surface 39M, andthe electrolytic solution include the methylene cyclic carbonate.Therefore, good battery characteristics are allowed to be obtainedbecause of a reason similar to that in the case of the prismatic typesecondary battery. Functions and effects other than this are similar tothose in the case of the prismatic type secondary battery.

(1-3. Lithium Metal Secondary Battery (Prismatic Type, Laminate FilmType))

A secondary battery described here is a lithium secondary battery(lithium metal secondary battery) in which the capacity of an anode isrepresented by deposition and dissolution of lithium (lithium metal) asan electrode reactant. The secondary battery has a configuration similarto that of the above-described prismatic type lithium-ion secondarybattery, except that the anode active material layer 22B is formed oflithium metal, and is manufactured by steps similar to those in the caseof the above-described prismatic type lithium-ion secondary battery.

In the secondary battery, as lithium metal is used as the anode activematerial, high energy density is allowed to be obtained. The anodeactive material layer 22B may exist at the time of assembling, or maynot exist at the time of assembling, and may be formed of lithium metaldeposited during charge. Moreover, the anode active material layer 22Bmay be also used as a current collector, and the anode current collector22A may not be included.

In the secondary battery, for example, lithium ions extracted from thecathode 21 are deposited as lithium metal on surfaces of the anodecurrent collector 22A through the electrolytic solution during charge.On the other hand, for example, lithium metal in the anode activematerial layer 22B is eluted as lithium ions into the electrolyticsolution, and the lithium ions are inserted into the cathode 21 throughthe electrolytic solution during discharge.

In the lithium metal secondary battery, the electrolytic solutionincludes the methylene cyclic carbonate; therefore, good batterycharacteristics are allowed to be obtained because of a reason similarto that in the case of the above-described lithium ion secondarybatteries. Functions and effects other than this are similar to those inthe case of the prismatic type secondary battery. It is to be noted thatthe lithium metal secondary battery is not limited to the prismatic typesecondary battery, and may be the laminate film type secondary batteryillustrated in FIGS. 3 and 4. In this case, similar effects are alsoallowed to be obtained.

Although some specific examples of the secondary battery are describedabove, the battery configuration of the secondary battery and the deviceconfiguration of the battery device may have any other configuration, aslong as the package member of the secondary battery has a flat surface.More specifically, for example, the battery configuration is not limitedto the prismatic type and the laminate film type, and may be a cointype, a button type, or the like. Moreover, the device configuration isnot limited to a spirally wound configuration, and may be a laminateconfiguration. In this case, similar effects are also allowed to beobtained.

2. Secondary Battery Second Embodiment

(2-1. Lithium-Ion Secondary Battery (Cylindrical Type))

Next, a secondary battery according to a second embodiment of thetechnology will be described below.

FIGS. 5 and 6 illustrate a sectional configuration of the secondarybattery, and FIG. 6 illustrates an enlarged view of a part of a spirallywound electrode body 40 illustrated in FIG. 5. A description will begiven of constituent components of the secondary battery with referenceto the above-described components of the secondary battery (prismatictype) according to the first embodiment as appropriate.

[Entire Configuration of Secondary Battery]

The secondary battery described here has a so-called cylindrical typebattery configuration. In the secondary battery, the spirally woundelectrode body 40 and a pair of insulating plates 32 and 33 arecontained in a substantially hollow cylindrical shaped battery can 31.The spirally wound electrode body 40 is formed, for example, bylaminating a cathode 41 and an anode 42 with a separator 43 in between,and then spirally winding them.

The battery can 31 has a hollow configuration in which an end of thebattery can 31 is closed and the other end thereof is opened, and thebattery can 31 is made of, for example, a material similar to that ofthe battery can 11. The pair of insulating plates 32 and 33 are disposedto allow the spirally wound electrode body 40 to be sandwichedtherebetween at the top and the bottom of the spirally wound electrodebody 40 and to extend in a direction perpendicular to a peripheralwinding surface.

In the open end of the battery can 31, a battery cover 34, and a safetyvalve mechanism 35, and a positive temperature coefficient (PTC) device36 are caulked by a gasket 37, thereby sealing the battery can 31. Thebattery cover 34 is made of, for example, a material similar to that ofthe battery can 31. The safety valve mechanism 35 and the PTC device 36are disposed inside the battery cover 34, and the safety valve mechanism35 is electrically connected to the battery cover 34 through the PTCdevice 36. In the safety valve mechanism 35, when an internal pressurein the secondary battery increases to a certain extent or higher due toan internal short circuit or external application of heat, a disk plate35A is flipped to disconnect the electrical connection between thebattery cover 34 and the spirally wound electrode body 40. The PTCdevice 36 prevents abnormal heat generation caused by a large current.The PTC device 36 increases resistance with an increase in temperature.The gasket 37 is made of, for example, an insulating material, and itssurface may be coated with asphalt.

A center pin 44 may be inserted into the center of the spirally woundelectrode body 40. A cathode lead 45 made of a conductive material suchas aluminum is connected to the cathode 41, and an anode lead 46 made ofa conductive material such as nickel is connected to the anode 42. Thecathode lead 45 is connected to the safety valve mechanism 35 by weldingor the like, and is electrically connected to the battery cover 34, andthe anode lead 46 is connected to the battery can 31 by welding or thelike, and is electrically connected to the battery can 31.

[Cathode, Anode and Separator]

The cathode 41 includes, for example, a cathode current collector 41Aand a cathode active material layer 41B disposed on both surfaces of thecathode current collector 41A. The anode 42 includes, for example, ananode current collector 42A and an anode active material layer 42Bdisposed on both surfaces of the anode current collector 42A. Theconfigurations of the cathode current collector 41A, the cathode activematerial layer 41B, the anode current collector 42A, and the anodeactive material layer 42B are similar to those of the cathode currentcollector 21A, the cathode active material layer 21B, the anode currentcollector 22A, and the anode active material layer 22B, respectively.Moreover, the configuration of the separator 43 is similar to that ofthe separator 23.

[Electrolytic Solution]

An electrolytic solution which is a liquid electrolyte is impregnatedwith the separator 43, and includes a methylene cyclic carbonaterepresented by the following expression (11) and one or more kindsselected from auxiliary compounds represented by the followingexpressions (12) to (16). However, the electrolytic solution may includeother materials such as a nonaqueous solvent and an electrolyte salt.

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygen-containing monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other.

where R71 and R73 each are a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, an oxygen-containing monovalenthydrocarbon group, or an oxygen-containing monovalent halogenatedhydrocarbon group, and R72 is a divalent hydrocarbon group, a divalenthalogenated hydrocarbon group, an oxygencontaining divalent hydrocarbongroup, or an oxygen-containing divalent halogenated hydrocarbon group.

where R74 and R76 each are a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, an oxygen-containing monovalenthydrocarbon group, or an oxygen-containing monovalent halogenatedhydrocarbon group, R75 is a divalent hydrocarbon group, a divalenthalogenated hydrocarbon group, an oxygen-containing divalent hydrocarbongroup, or an oxygen-containing divalent halogenated hydrocarbon group,and n is an integer of 1 or more.

where R77 and R79 each are a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, an oxygen-containing monovalenthydrocarbon group, or an oxygen-containing monovalent halogenatedhydrocarbon group, and R78 is a divalent hydrocarbon group, a divalenthalogenated hydrocarbon group, an oxygen-containing divalent hydrocarbongroup, or an oxygen-containing divalent halogenated hydrocarbon group.

Li₂PFO₃  (15)

LiPF₂O₂  (16)

The electrolytic solution includes both the methylene cyclic carbonateand the auxiliary compound, because chemical stability of theelectrolytic solution is improved by a synergistic interaction betweenthem. Therefore, a reduction in discharge capacity is less likely tooccur, even if the secondary battery is repeatedly charged anddischarged and the secondary battery is kept in a high-temperatureenvironment.

Details of the methylene cyclic carbonate represented by the expression(11) is similar to those of the methylene cyclic carbonate representedby the expression (1) in the first embodiment, and will not be furtherdescribed.

The auxiliary compound represented by the expression (12) is adicarbonate compound having carbonate groups (—O—C(═O)—O—R71 and—O—C(═O)—O—R73) at both ends.

Kinds of R71 and R73 are not specifically limited, as long as they eachare a monovalent hydrocarbon group, a monovalent halogenated hydrocarbongroup, an oxygen-containing monovalent hydrocarbon group, or anoxygen-containing monovalent halogenated hydrocarbon group, as describedabove, because the dicarbonate compound has the carbonate groups,thereby allowing the above-described advantages to be obtained withoutrelying on the kinds of R71 and R73. It is to be noted that the kinds ofR71 and R73 may be the same as or different from each other.

Examples of the monovalent hydrocarbon group and the monovalenthalogenated hydrocarbon group include an alkyl group having 1 to 12carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynylgroup having 2 to 12 carbon atoms, an aryl group having 6 to 18 carbonatoms, a cycloalkyl group having 3 to 18 carbon atoms, and a group inwhich one or more of hydrogen groups in any of the above-describedgroups is substituted with a halogen group. Moreover, examples of theoxygen-containing monovalent hydrocarbon group and the oxygen-containingmonovalent halogenated hydrocarbon group include an alkoxy group having1 to 12 carbon atoms, and a group in which one or more of hydrogengroups in the alkoxy group is substituted with a halogen group, becausethe above-described advantages are obtainable while securing solubility,compatibility, and the like of the dicarbonate compound. It is to benoted that the alkyl group, the alkenyl group, the alkynyl group, or thealkoxy group may have a straight-chain structure, or a branchedstructure having one or two or more side chains. For example, details ofR71 and R73 are similar to those of R1 and R2 in the first embodiment,and will not be further described.

The kind of R72 is not specifically limited, as long as R72 is adivalent hydrocarbon group, a divalent halogenated hydrocarbon group, anoxygen-containing divalent hydrocarbon group, or an oxygen-containingdivalent halogenated hydrocarbon group, as described above, because theabove-described advantages are obtainable without relying on the kind ofR72 by a reason similar to the abovedescribed reason in the case of R71and R73.

Examples of the divalent hydrocarbon group include an alkylene grouphaving 1 to 12 carbon atoms, an alkenylene group having 2 to 12 carbonatoms, an alkynylene group having 2 to 12 carbon atoms, an arylene grouphaving 6 to 18 carbon atoms, a cycloalkylene group having 3 to 18 carbonatoms, and a group including an arylene group and an alkylene group.However, the group including an arylene group and an alkylene group maybe a group in which one arylene group and one alkylene group are linkedto each other, or a group (an aralkylene group) in which two alkylenegroups are linked to each other through an arylene group. The number ofcarbon atoms in the alkylene group is preferably 12 or less. Moreover,the divalent halogenated hydrocarbon group is, for example, a group inwhich one or more of hydrogen groups in the above-described alkylenegroup or the like is substituted with a halogen group, because theabove-described advantages are obtainable while securing solubility,compatibility, and the like of the dicarbonate compound.

Examples of the oxygen-containing divalent hydrocarbon group include agroup including an ether bond and an alkylene group. However, the groupincluding an ether bond and an alkylene group may be a group in whichone ether bond and one alkylene group are linked to each other, or agroup (an aralkylene group) in which two alkylene groups are linked toeach other through one ether bond. The number of carbon atoms in thealkylene group is preferably 12 or less. Moreover, examples of theoxygen-containing divalent halogenated hydrocarbon group include a groupin which one or more of hydrocarbon groups in the above-described groupincluding an ether bond and an alkylene group, or the like issubstituted with a halogen group, because the above-described advantagesare obtainable while securing solubility, compatibility, and the like ofthe dicarbonate compound.

Specific examples of R72 include straight-chain alkylene groupsrepresented by the following expressions (12-1) to (12-7), branchedalkylene groups represented by expressions (12-8) to (12-16), arylenegroups represented by expressions (12-17) to (12-19), and divalentgroups (benzylidene groups) including an arylene group and an alkylenegroup represented by expressions (12-20) to (12-22).

It is to be noted that as the divalent group including an ether bond andan alkylene group, a group in which two or more alkylene groups arelinked to each other through an ether bond and carbon atoms are includedat both ends thereof is preferable. The number of carbon atoms in such agroup is preferably within a range of 4 to 12 both inclusive, becausegood solubility and good compatibility are obtainable. However, thenumber of ether bonds, the linking order of the ether bond and thealkylene groups may be arbitrarily selected.

Specific examples of R72 in this case include divalent groupsrepresented by the following expressions (12-23) to (12-35). Moreover,in the case where the divalent groups represented by the expressions(12-23) to (12-35) are fluorinated, examples of R72 may include groupsrepresented by expressions (12-36) to (12-44). In particular, the groupsrepresented by the expressions (12-28) to (12-30) are preferable.

The molecular weight of the dicarbonate compound is not specificallylimited, but is preferably within a range of 200 to 800 both inclusive,more preferably within a range of 200 to 600 both inclusive, and stillmore preferably within a range of 200 to 450 both inclusive, becausegood solubility and good compatibility are obtainable.

Specific examples of the dicarbonate compound include compoundsrepresented by the following expressions (12-45) to (12-56), becausesufficient solubility and sufficient compatibility are obtainable, andchemical stability of the electrolytic solution is sufficientlyimproved. However, any other compound corresponding to the expression(12) may be used.

The auxiliary compound represented by the expression (13) is adicarboxylic acid compound having carboxylic acid groups (—O—C(═O)—R74and —O—C(═O)—R76) at both ends. The value of n is not specificallylimited, as long as the value is an integer of 1 or more. The kinds ofR74 and R76 may be the same as or different from each other. It is to benoted that details of R74 to R76 are similar to those of R71 to R73, andwill not be further described.

The molecular weight of the dicarboxylic acid compound is notspecifically limited, but is preferably within a range of 162 to 1000both inclusive, more preferably within a range of 162 to 500 bothinclusive, and still more preferably within a range of 162 to 300 bothinclusive, because good solubility and good compatibility areobtainable.

Specific examples of the dicarboxylic acid compound include compoundsrepresented by the following expressions (13-1) to (13-17), becausesufficient solubility and sufficient compatibility are obtainable, andchemical stability of the electrolytic solution is sufficientlyimproved. However, any other compound corresponding to the expression(13) may be used.

The auxiliary compound represented by the expression (14) is adifulfonic acid compound having sulfonic acid groups (—O—S(═O)₂—R77 and—O—S(═O)₂—R79) at both ends. The kinds of R77 and R79 may be the same asor different from each other. It is to be noted that details of R77 toR79 are similar to those of R71 to R73, and will not be furtherdescribed.

The molecular weight of the disulfonic acid compound is not specificallylimited, but is preferably within a range of 200 to 800 both inclusive,more preferably within a range of 200 to 600 both inclusive, and stillmore preferably within a range of 200 to 450 both inclusive, becausegood solubility and good compatibility are obtainable.

Specific examples of the disulfonic acid compound include compoundsrepresented by the following expressions (14-1) to (14-9), becausesufficient solubility and sufficient compatibility are obtainable, andchemical stability of the electrolytic solution is sufficientlyimproved. However, any other compound corresponding to the expression(14) may be used.

The auxiliary compound represented by the expression (15) is lithiummonofluorophosphate, and the auxiliary compound represented by theexpression (16) is lithium difluorophosphate.

The content of the methylene cyclic carbonate in the electrolyticsolution is not specifically limited, but is preferably within a rangeof 0.01 wt % to 10 wt % both inclusive, and more preferably within arange of 0.5 wt % to 5 wt % both inclusive. Moreover, the content of theauxiliary compound in the electrolytic solution is not specificallylimited, but is preferably within a range of 0.001 wt % to 2 wt % bothinclusive, and more preferably within a range of 0.1 wt % to 1 wt % bothinclusive, because a higher effect is obtainable.

It is to be noted that details of the nonaqueous solvent and theelectrolyte salt are similar to those in the first embodiment, and willnot be further described.

[Operation of Secondary Battery]

In the secondary battery, for example, lithium ions extracted from thecathode 41 are inserted into the anode 42 through the electrolyticsolution during charge, and lithium ions extracted from the anode 42 areinserted into the cathode 41 through the electrolytic solution duringdischarge.

[Method of Manufacturing Secondary Battery]

The secondary battery is manufactured by, for example, the followingsteps.

First, the cathode 41 and the anode 42 are formed by steps similar tothose in the first embodiment. In this case, the cathode active materiallayer 41B is formed on both surfaces of the cathode current collector41A to form the cathode 41, and the anode active material layer 42B isformed on both surfaces of the anode current collector 42A to form theanode 42.

Moreover, the electrolyte salt is dispersed in the nonaqueous solvent,and then the methylene cyclic carbonate and the auxiliary compound areadded to the nonaqueous solvent to prepare the electrolytic solution.

Finally, the secondary battery is assembled with use of the cathode 41and the anode 42. The cathode lead 45 and the anode lead 46 are attachedto the cathode current collector 41A and the anode current collector42A, respectively, by a welding method or the like. Next, the cathode 41and the anode 42 are laminated with the separator 43 in between, andthey are spirally wound to form the spirally wound electrode body 40,then the center pin 44 is inserted into the center of the spirally woundelectrode body 40. Next, the spirally wound electrode body 40 sandwichedbetween the pair of insulating plates 32 and 33 is contained in thebattery can 31. In this case, the safety valve mechanism 35 and thebattery can 31 are attached to an end of the cathode lead 45 and an endof the anode lead 46, respectively, by a welding method or the like.Then, the electrolytic solution is injected into the battery can 31 toimpregnate the separator 43 with the electrolytic solution. Next, thebattery cover 34, the safety valve mechanism 35, and the PTC device 36are caulked in the open end of the battery can 31 by the gasket 37.

[Functions and Effects of Secondary Battery]

In the cylindrical type secondary battery, the electrolytic solutionincludes the methylene cyclic carbonate and the auxiliary compound. Inthis case, as described above, chemical stability of the electrolyticsolution is improved by a synergistic interaction between them;therefore, a reduction in discharge capacity is less likely to occur,even if the secondary battery is repeatedly charged and discharged andthe secondary battery is kept in a high-temperature environment.Accordingly, good battery characteristics are allowed to be obtained.

In particular, when the content of the methylene cyclic carbonate in theelectrolytic solution is within a range of 0.01 wt % to 10 wt % bothinclusive, specifically within a range of 0.5 wt % to 5 wt % bothinclusive, a higher effect is allowed to be obtained. Moreover, when thecontent of the auxiliary compound in the electrolytic solution is withina range of 0.001 wt % to 2 wt % both inclusive, specifically within arange of 0.1 wt % to 1 wt % both inclusive, a higher effect is allowedto be obtained.

(2-2. Lithium-Ion Secondary Battery (Prismatic Type, Laminate FilmType))

It is to be noted that the secondary battery according to the embodimentmay be a prismatic type secondary battery, a laminate film typesecondary battery, or the like, instead of the above-describedcylindrical type secondary battery. The configuration of the prismatictype or laminate film type secondary battery is similar to that in thefirst embodiment, except that the composition of the electrolyticsolution is different from that in the first embodiment. In this case,good battery characteristics are also allowed to be obtained.

(2-3. Lithium Metal Secondary Battery (Cylindrical Type, Prismatic Type,Laminate Film Type))

Moreover, the secondary battery according to the embodiment may be alithium metal secondary battery instead of the above-describedlithium-ion secondary battery. In this case, the secondary battery may acylindrical type, a prismatic type, or a laminate film type secondarybattery. The configuration of the lithium metal secondary battery issimilar to that in the first embodiment, except that the configurationof the anode is different from that in the first embodiment. In thiscase, good battery characteristics are also allowed to be obtained.

3. Secondary Battery Third Embodiment

3-1. Lithium-Ion Secondary Battery (Cylindrical Type))

Next, a secondary battery according to a third embodiment of thetechnology will be described below.

The secondary battery according to the embodiment has a configurationsimilar to that in the second embodiment, except that, for example, thecomposition of the electrolytic solution is different from that in thesecond embodiment. In other words, the secondary battery described hereis a cylindrical type lithium-ion secondary battery.

The electrolytic solution includes a methylene cyclic carbonaterepresented by the following expression (17) and one or both ofhalogenated carbonates represented by the following expressions (18) and(19). However, the electrolytic solution may include any other materialsuch as a nonaqueous solvent and an electrolyte salt.

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, or a monovalent halogenated hydrocarbon group, and R1and R2 may be bonded to each other.

where R17 to R20 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R17 to R20 is a halogen group or a monovalenthalogenated hydrocarbon group.

where R21 to R26 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R21 to R26 is a halogen group or a monovalenthalogenated hydrocarbon group.

The electrolytic solution includes both the methylene cyclic carbonateand the halogenated carbonate, because chemical stability of theelectrolytic solution is improved by a synergistic interaction betweenthem. Therefore, a reduction in discharge capacity is less likely tooccur, even if the secondary battery is repeatedly charged anddischarged and the secondary battery is kept in a high-temperatureenvironment.

Details of the methylene cyclic carbonate represented by the expression(17) is similar to those of the methylene cyclic carbonate in the firstembodiment, and will not be further described. Moreover, details of thehalogenated carbonates represented by the expressions (18) and (19) aresimilar to those of the halogenated carbonates (the halogenated cycliccarbonate and the halogenated chain carbonate) in the first embodiment,and will not be further described.

The content of the methylene cyclic carbonate in the electrolyticsolution is not specifically limited, but is preferably within a rangeof 0.01 wt % to 10 wt % both inclusive, and more preferably within arange of 0.1 wt % to 5 wt % both inclusive. Moreover, the content of thehalogenated carbonate in the electrolytic solution is not specificallylimited, but is preferably within a range of 0.1 wt % to 20 wt % bothinclusive, and more preferably within a range of 5 wt % to 20 wt % bothinclusive, because a higher effect is obtainable.

It is to be noted that details of the nonaqueous solvent and theelectrolyte salt are similar to those in the first embodiment, and willnot be further described.

For example, details of the operation and the manufacturing method ofthe secondary battery are similar to those in the second embodiment(cylindrical type), except that the composition of the electrolyticsolution is different from that in the second embodiment.

In the cylindrical type secondary battery, the electrolytic solutionincludes the methylene cyclic carbonate and the halogenated carbonate.In this case, as described above, chemical stability of the electrolyticsolution is improved by the synergistic interaction between them;therefore, a reduction in discharge capacity is less likely to occur,even if the secondary battery is repeatedly charged and discharged andthe secondary battery is kept in a high-temperature environment.Accordingly, good battery characteristics are allowed to be obtained.

In particular, when the content of the methylene cyclic carbonate in theelectrolytic solution is within a range of 0.01 wt % to 10 wt % bothinclusive, and the content of the halogenated carbonate in theelectrolytic solution is within a range of 0.1 wt % to 20 wt % bothinclusive, a higher effect is allowed to be obtained.

(3-2. Lithium-Ion Secondary Battery (Prismatic Type, Laminate FilmType))

It is to be noted that the secondary battery according to the embodimentmay be a prismatic type secondary battery, a laminate film typesecondary battery, or the like, instead of the above-describedcylindrical type secondary battery. The configuration of the prismatictype or laminate film type secondary battery is similar to that in thefirst embodiment, except that the composition of the electrolyticsolution is different from that in the first embodiment. In this case,good battery characteristics are also allowed to be obtained.

(3-3. Lithium Metal Secondary Battery (Cylindrical Type, Prismatic Type,Laminate Film Type))

Moreover, the secondary battery according to the embodiment may be alithium metal secondary battery instead of the above-describedlithium-ion secondary battery. In this case, the secondary battery may acylindrical type, a prismatic type, or a laminate film type secondarybattery. The configuration of the lithium metal secondary battery issimilar to that in the first embodiment, except that the configurationof the anode is different from that in the first embodiment. In thiscase, good battery characteristics are also allowed to be obtained.

4. Secondary Battery Fourth Embodiment

4-1. Lithium-Ion Secondary Battery (Cylindrical Type))

Next, a secondary battery according to a fourth embodiment of thetechnology will be described below.

The secondary battery according to the embodiment has a configurationsimilar to that in the second embodiment, except that, for example, thecomposition of the electrolytic solution is different from that in thesecond embodiment. In other words, the secondary battery described hereis a cylindrical type lithium-ion secondary battery.

The electrolytic solution includes one or more kinds of methylene cycliccarbonates represented by the following expressions (20) to (22).However, the electrolytic solution may include any other material suchas a nonaqueous solvent and an electrolyte salt.

where R81 is a monovalent chain unsaturated hydrocarbon group, amonovalent chain halogenated unsaturated hydrocarbon group, a halogengroup, or a monovalent chain halogenated saturated hydrocarbon group.

where R82 and R83 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, a monovalent halogenated hydrocarbongroup, an oxygen-containing monovalent hydrocarbon group, or anoxygen-containing monovalent halogenated hydrocarbon group, and one orboth of R82 and R83 may be a monovalent cyclic hydrocarbon group or amonovalent halogenated cyclic hydrocarbon group.

where R84 is a divalent hydrocarbon group or a divalent halogenatedhydrocarbon group.

The electrolytic solution includes the methylene cyclic carbonate,because compared to the case where the methylene cyclic carbonate is notincluded, chemical stability of the electrolytic solution is improved.Therefore, a reduction in discharge capacity is less likely to occur,even if the secondary battery is repeatedly charged and discharged andthe secondary battery is kept in a high-temperature environment.

More specifically, in the methylene cyclic carbonate represented by theexpression (20), R81 is a hydrogen group, or a chain saturatedhydrocarbon group such as a methyl group, chemical stability of theelectrolytic solution is not sufficient; therefore, the electrolyticsolution is easily decomposed during charge and discharge or duringstorage in a high-temperature environment. On the other hand, when R81is the above-described monovalent chain unsaturated hydrocarbon group orthe like, chemical stability of the electrolytic solution is secured.Therefore, the electrolytic solution is less likely to be decomposedduring charge and discharge or during storage in a high-temperatureenvironment.

Moreover, in the methylene cyclic carbonate represented by theexpression (21), R82 and R83 both are monovalent chain hydrocarbongroups such as methyl groups, the electrolytic solution is easilydecomposed during charge and discharge or during storage in ahigh-temperature environment due to a reason similar to that in the caseof the expression (20). On the other hand, when one or both of R82 andR83 are the above-described monovalent cyclic hydrocarbon groups or thelike, chemical stability of the electrolytic solution is secured;therefore, the electrolytic solution is less likely to be decomposedduring charge and discharge or during storage in a high-temperatureenvironment.

Further, in the cyclic carbonate represented by the expression (22), aring structure including R84 as a part is formed; therefore, chemicalstability of the electrolytic solution is improved, compared to the casewhere the ring structure is not formed. Thus, the electrolytic solutionis less likely to be decomposed during charge and discharge or duringstorage in a high-temperature environment.

Details of the methylene cyclic carbonates represented by theexpressions (20) to (22) are similar to the methylene cyclic carbonatein the first embodiment, except for points which will be describedbelow.

The kind of R81 is not specifically limited, as long as R81 is amonovalent chain unsaturated hydrocarbon group, a monovalent chainhalogenated unsaturated hydrocarbon group, a halogen group, or amonovalent chain halogenated saturated hydrocarbon group, because themethylene cyclic carbonate has a cyclic carbonate structure including amonovalent chain unsaturated hydrocarbon group or the like, therebyallowing the above-described advantages to be obtained without relyingon the kind of R81.

The “monovalent chain unsaturated hydrocarbon group” is a chainhydrocarbon group including an unsaturated carbon bond such as acarbon-carbon double bond or a carbon-carbon triple bond at an end of acarbon chain or in the middle of the carbon chain. Moreover, the“monovalent chain halogenated unsaturated hydrocarbon group” is a groupin which one or more of hydrogen groups in the abovedescribed monovalentchain unsaturated hydrocarbon group is substituted with a halogen group.However, the number of unsaturated carbon bonds may be one or two ormore. Moreover, the monovalent chain halogenated unsaturated hydrocarbongroup may have a straight-chain structure, or a branched structurehaving one or two or more side chains. Examples of the monovalent chainunsaturated hydrocarbon group include an alkenyl group having 2 to 12carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an arylgroup having 6 to 18 carbon atoms, a group in which an aryl group having6 to 18 carbon atoms and an alkylene group having 1 to 12 carbon atomsare bonded to each other, and a group in which a hydrogen group in themiddle of an alkyl group having 1 to 12 carbon atoms is substituted withan aryl group having 6 to 18 carbon atoms. In addition, a group in whichan alkyl group having 1 to 12 carbon atoms and an alkylene group having1 to 12 carbon atoms are bonded to each other through an arylene grouphaving 6 to 18 carbon atoms may be used. Moreover, examples of themonovalent chain halogenated unsaturated hydrocarbon group include agroup in which one or more of hydrogen groups in the above-describedalkyl group or the like is substituted with a halogen group. It is to benoted that details of the above-described alkyl group, theabove-described alkenyl group, the above-described alkynyl group, theabove-described aryl group, the above-described alkylene group, theabove-described halogen group, and the like are similar to those in thefirst embodiment.

The kinds of R82 and R83 are not specifically limited, as long as R82and R83 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygen-containing monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, as described above. However,as a condition, one or both of R82 and R83 are a monovalent cyclichydrocarbon group or a monovalent halogenated cyclic hydrocarbon group,because the methylene cyclic carbonate has a cyclic carbonate structureincluding one or more monovalent cyclic carbonate groups, or the like,thereby allowing the above-described advantages to be obtained withoutrelying on the kinds of R82 and R83.

The “monovalent cyclic hydrocarbon group” is a hydrocarbon group havinga saturated ring structure or an unsaturated ring structure, and the“monovalent halogenated cyclic hydrocarbon group” is a group in whichone or more of hydrogen groups in the above-described monovalent cyclichydrocarbon group is substituted with a halogen group. Moreover, the“monovalent hydrocarbon group” includes both of the saturatedhydrocarbon group and the unsaturated hydrocarbon group, and the sameapplies to the “monovalent halogenated hydrocarbon group”. Examples ofthe monovalent cyclic hydrocarbon group include an aryl group having 6to 18 carbon atoms, a group in which an aryl group having 6 to 18 carbonatoms and an alkylene group having 1 to 12 carbon atoms are bonded toeach other, a cycloalkyl group having 6 to 18 carbon atoms, and a groupin which a cycloalkyl group having 6 to 18 carbon atoms and an alkylenegroup having 1 to 12 carbon atoms are bonded to each other. In addition,a group in which an alkyl group having 1 to 12 carbon atoms and analkylene group having 1 to 12 carbon atoms are bonded to each otherthrough an arylene group or a cycloalkyl group having 6 to 18 carbonatoms may be used. Moreover, examples of the monovalent halogenatedcyclic hydrocarbon group include a group in which one or more ofhydrogen groups in the above-described aryl group or the like issubstituted with a halogen group. It is to be noted that details of theabove-described aryl group, the above-described cycloalkyl group, theabove-described halogen group, and the like are similar to those in thefirst embodiment.

In the methylene cyclic carbonate represented by the expression (22),the kind of R84 is not specifically limited, as long as R84 is adivalent hydrocarbon group or a divalent halogenated hydrocarbon group,as described above, because the methylene cyclic carbonate has a cycliccarbonate structure including a ring structure formed by including R84as a part together with a methylene group, thereby allowing theabovedescribed advantages to be obtained without relying on the kind ofR84.

Examples of the divalent hydrocarbon group include an alkylene grouphaving 2 to 12 carbon atoms, and specific examples thereof include abutylene group and a pentyl group. However, the alkylene group may havea straight-chain structure, or a branched structure having one or two ormore side chains. Moreover, examples of the divalent halogenatedhydrocarbon group include a group in which one or more of hydrogengroups in the above-described alkylene group or the like is substitutedwith a halogen group, because the above-described advantages areobtainable while securing solubility, compatibility, and the like of themethylene cyclic carbonate. It is to be noted that details of theabove-described alkylene group, the above-described halogen group, andthe like are similar to those in the first embodiment.

It is to be noted that R81 to R84 each may be any kind of group otherthan the above-described groups. Specific examples of R81 to R84 includederivatives of the above-described groups. The derivative is a groupformed by introducing one or two or more substituent groups into any ofthe above-described groups, and the kind of the substituent group isarbitrarily selected.

Specific examples of the methylene cyclic carbonate represented by theexpression (20) include the compounds represented by the expressions(1-4), (1-13), (1-18), (1-20), (1-22), (1-23), and (1-30) in thecompounds represented by the expressions (1-1) to (1-31) in the firstembodiment.

Specific examples of the methylene cyclic carbonate represented by theexpression (21) include the compounds represented by the expressions(1-3), (1-5), (1-6), (1-10) to (1-12), (1-14), (1-16), (1-17), and(1-24).

Specific examples of the methylene cyclic carbonate represented by theexpression (22) include the compounds represented by the expressions(1-28), (1-29), and (1-31).

The content of the methylene cyclic carbonate in the electrolyticsolution is not specifically limited, but is preferably within a rangeof 0.01 wt % to 10 wt % both inclusive.

It is to be noted that details of the nonaqueous solvent and theelectrolyte salt are similar to those in the first embodiment, and inparticular, the electrolytic solution preferably includes the auxiliarycompound described in the second embodiment, because a higher effect isobtainable. The kind and content of the auxiliary compound have beenalready described in detail above, and will not be further described.Moreover, for example, details of the operation and the manufacturingmethod of the secondary battery are similar to those in the secondembodiment (cylindrical type), except that the composition of theelectrolytic solution is different from that in the second embodiment.

In the cylindrical type secondary battery, as the electrolytic solutionincludes the methylene cyclic carbonate, chemical stability of theelectrolytic solution is improved. Therefore, a reduction in dischargecapacity is less likely to occur, even if the secondary battery isrepeatedly charged and discharged and the secondary battery is kept in ahigh-temperature environment. Accordingly, good battery characteristicsare allowed to be obtained.

In particular, when the content of the methylene cyclic carbonate in theelectrolytic solution is within a range of 0.01 wt % to 10 wt % bothinclusive, a higher effect is allowed to be obtained. Moreover, when theelectrolytic solution includes the auxiliary compound with the methylenecyclic carbonate, a higher effect is allowed to be obtained.

(4-2. Lithium-Ion Secondary Battery (Prismatic Type, Laminate FilmType))

It is to be noted that the secondary battery according to the embodimentmay be a prismatic type secondary battery, a laminate film typesecondary battery, or the like, instead of the above-describedcylindrical type secondary battery. The configuration of the prismatictype or laminate film type secondary battery is similar to that in thefirst embodiment, except that the composition of the electrolyticsolution is different from that in the first embodiment. In this case,good battery characteristics are also allowed to be obtained.

(4-3. Lithium Metal Secondary Battery (Cylindrical Type, Prismatic Type,Laminate Film Type))

Moreover, the secondary battery according to the embodiment may be alithium metal secondary battery, instead of the above-describedlithium-ion secondary battery. In this case, the secondary battery maybe a cylindrical type, a prismatic type, or a laminate film typesecondary battery. The configuration of the lithium metal secondarybattery is similar to that in the first embodiment, except that theconfiguration of the anode is different from that in the firstembodiment. In this case, good battery characteristics are also allowedto be obtained.

5. Secondary Battery Fifth Embodiment

5-1. Lithium-Ion Secondary Battery (Cylindrical Type))

Next, a secondary battery according to a fifth embodiment of thetechnology will be described below.

The secondary battery according to the embodiment has a configurationsimilar to that in the second embodiment, except that, for example, thecomposition of the electrolytic solution is different from that in thesecond embodiment. In other words, the secondary battery described hereis a cylindrical type lithium-ion secondary battery.

The electrolytic solution includes a methylene cyclic carbonaterepresented by the following expression (23) and an unsaturated cycliccarbonate represented by the following expression (24). It is clear fromthe expression (24) that the unsaturated cyclic carbonate in theembodiment is a vinylene carbonate-based compound. However, theelectrolytic solution may include any other material such as anonaqueous solvent and an electrolyte salt.

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, or a monovalent halogenated hydrocarbon group, and R1and R2 may be bonded to each other.

where R11 and R12 each are a hydrogen group or an alkyl group.

Details of the methylene cyclic carbonate represented by the expression(23) are similar to those of the methylene cyclic carbonate in the firstembodiment, and will not be further described. Moreover, details of theunsaturated cyclic carbonate represented by the expression (24) aresimilar to those of the unsaturated cyclic carbonate (vinylenecarbonate-based compound) in the first embodiment, and will not befurther described.

However, the contents of the methylene cyclic carbonate and theunsaturated cyclic carbonate and a mixture thereof satisfy predeterminedconditions. More specifically, it is assumed that the content of theunsaturated cyclic carbonate in the electrolytic solution is A (wt %)and the content of the methylene cyclic carbonate in the electrolyticsolution is B (wt %). In this case, three conditions: that A be equal to0.01 wt % to 5 wt % both inclusive; that B be equal to 0.01 wt % to 5 wt% both inclusive; and that B/A be equal to 0.002 to 500 both inclusiveare concurrently satisfied. The kind of the unsaturated cyclic carbonateis not specifically limited, as long as the unsaturated cyclic carbonatehas a chemical structure represented by the expression (24). Specificexamples of the unsaturated cyclic carbonate is one kind or two or morekinds selected from the group consisting of vinylene carbonate(1,3-dioxol-2-one), methyl vinylene carbonate(4-methyl-1,3-dioxol-2-one), and the like.

The electrolytic solution includes both the methylene cyclic carbonateand the unsaturated cyclic carbonate, because chemical stability of theelectrolytic solution is improved by a synergistic interaction betweenthem. Therefore, a reduction in discharge capacity is less likely tooccur, even if the secondary battery is repeatedly charged anddischarged and the secondary battery is kept in a high-temperatureenvironment. Moreover, it is because when the contents of the methylenecyclic carbonate and the unsaturated cyclic carbonate and the mixtureratio thereof satisfy the predetermined conditions, chemical stabilityof the electrolytic solution is further improved. Therefore, a reductionin discharge capacity is less likely to occur, even if the secondarybattery is repeatedly charged and discharged under a load condition (forexample, high current). Such a tendency is pronounced when the secondarybattery is charged and discharged specifically in a severe temperatureenvironment such as low temperature.

It is to be noted that details of the nonaqueous solvent and theelectrolyte salt are similar to those in the first embodiment, and willnot be further described.

For example, details of the operation and the manufacturing method ofthe secondary battery are similar to those in the second embodiment(cylindrical type), except that the composition of the electrolyticsolution is different from that in the second embodiment.

In the cylindrical type secondary battery, the electrolytic solutionincludes both the methylene cyclic carbonate and the unsaturated cycliccarbonate, and the contents A and B and the ratio B/A satisfy thepredetermined conditions. In this case, as described above, chemicalstability of the electrolytic solution is remarkably improved;therefore, a reduction in discharge capacity is less likely to occur,even if the secondary battery is kept in a high-temperature environmentor the secondary battery is charged and discharged under the loadcondition. Accordingly, good battery characteristics are allowed to beobtained.

(5-2. Lithium-Ion Secondary Battery (Prismatic Type, Laminate FilmType))

It is to be noted that the secondary battery according to the embodimentmay be a prismatic type secondary battery, a laminate film typesecondary battery, or the like, instead of the above-describedcylindrical type secondary battery. The configuration of the prismatictype or laminate film type secondary battery is similar to that in thefirst embodiment, except that the composition of the electrolyticsolution is different from that in the first embodiment. In this case,good battery characteristics are also allowed to be obtained.

(5-3. Lithium Metal Secondary Battery (Cylindrical Type, Prismatic Type,Laminate Film Type))

Moreover, the secondary battery according to the embodiment may be alithium metal secondary battery, instead of the above-describedlithium-ion secondary battery. In this case, the secondary battery maybe a cylindrical type, a prismatic type, or a laminate film typesecondary battery. The configuration of the lithium metal secondarybattery is similar to that in the first embodiment, except that theconfiguration of the anode is different from that in the firstembodiment. In this case, good battery characteristics are also allowedto be obtained.

Conditions of the composition of the electrolytic solution in theembodiment (the contents A and B and the ratio B/A) may be applied tothe above-described secondary batteries according to the first to fourthembodiments. In other words, in the case where, in the secondarybatteries according to the first to fourth embodiments, the electrolyticsolution includes the unsaturated cyclic carbonate, similar effects areallowed to be obtained when the contents A and B and the ratio B/Asatisfy the above-described conditions.

6. Appropriate Adjustment of Composition of Electrolytic Solution

Next, appropriate adjustment of the composition of the electrolyticsolution applied to the above-described secondary batteries according tothe first to fifth embodiments of the technology will be describedbelow.

It is preferable to appropriately adjust specific conditions of thecomposition of the electrolytic solution according to the kinds andcombinations of components of the electrolytic solution, because areduction in discharge capacity is suppressed, even if the secondarybattery is repeatedly charged and discharged under a load condition (forexample, high current). Such a tendency is pronounced when the secondarybattery is charged and discharged specifically in a severe temperatureenvironment such as low temperature.

Firstly, in the case where the electrolytic solution includes one orboth of the halogenated carbonates (one or both of the halogenatedcyclic carbonate and the halogenated chain carbonate) represented by theexpressions (4) and (5), it is preferable to appropriately adjust thecontents of the halogenated carbonate and the methylene cyclic carbonateand the ratio thereof. More specifically, it is assumed that the contentof the halogenated carbonate in the electrolytic solution is C (wt %),and the content of the methylene cyclic carbonate in the electrolyticsolution is D (wt %). In this case, it is preferable to concurrentlysatisfy three conditions: that C be equal to 0.01 wt % to 30 wt % bothinclusive; that D be equal to 0.01 wt % to 5 wt % both inclusive; andthat the ratio D/C be equal to 1/3000 to 500 both inclusive. The kind ofthe halogenated carbonate is not specifically limited, as long as thehalogenated carbonate has a chemical structure represented by theexpression (4) or (5). Specific examples of the halogenated carbonate isone kind or two or more kinds selected from the group consisting of4-fluoro-1,3-dioxolane-2-one and the like.

Secondly, in the case where the electrolytic solution includes bothethylene carbonate (1,3-dioxolane-2-one) and propylene carbonate(4-methyl-1,3-dioxolane-2-one), it is preferable to appropriately adjustthe mixture ratio of the ethylene carbonate and the propylene carbonateand the content of the methylene cyclic carbonate. More specifically, itis preferable to concurrently satisfy two conditions: that the mixtureratio of ethylene carbonate:propylene carbonate in weight ratio bewithin a range of 75:25 to 25:75 both inclusive; and that the content ofthe methylene cyclic carbonate in the electrolytic solution be within arange of 0.01 wt % to 10 wt % both inclusive.

7. Applications of Secondary Batteries

Next, application examples of any of the above-described secondarybatteries will be described below.

The application of any of the secondary batteries is not specificallylimited, as long as any of the secondary batteries is applied tomachines, devices, appliances, units, systems (combinations of aplurality of devices), and the like which each are allowed to use any ofthe secondary batteries as a power supply for drive or a power storagesource for power storage. In the case where any of the secondarybatteries is used as a power supply, the power supply may be a mainpower supply (a power supply to be preferentially used) or an auxiliarypower supply (a power supply to be used instead of the main power supplyor by switching from the main power supply). The kind of the main powersupply in the latter case is not limited to secondary batteries.

The secondary batteries are applied to, for example, the followingapplications. The applications include portable electronic units such asvideo cameras, digital still cameras, cellular phones, notebook personalcomputers, cordless telephones, headphone stereos, portable radios,portable televisions, and personal digital assistants. The electronicunits are not limited to portable electronic units. The applicationsfurther include portable home appliances such as electric shavers,memory units such as backup power supplies and memory cards, electricpower tools such as electric drills and electric saws, battery packsused as power supplies of notebook personal computers, medicalelectronic units such as pacemakers and hearing aids, electric vehiclessuch as electric cars (including hybrid vehicles), and energy storagesystem such as household battery systems storing power in case ofemergency or the like. The secondary batteries may be applied to anyapplications other than the above-described applications.

In particular, the secondary batteries are effectively applied to thebattery packs, the electric vehicles, the energy storage systems, theelectric power tools, the electronic units, and the like, because theyneed good battery characteristics, and their characteristics are allowedto be effectively improved by using the secondary battery according toany of the embodiments of the technology. It is to be noted that thebattery packs are power supplies using any of the secondary batteries,and are so-called assembled batteries or the like. The electric vehiclesare vehicles operating (running) with use of any of the secondarybatteries as a power supply for drive, and as described above, theelectric vehicles may include vehicles (such as hybrid vehicles)including a driving source in addition to the secondary battery. Theenergy storage systems are systems using any of the secondary batteriesas a power storage source. For example, in a household energy storagesystem, power is stored in any of the secondary batteries as a powerstorage source, and the power is consumed when necessary, therebyallowing home appliances or the like to be used by the household energystorage system. The electric power tools are tools having a movablesection (such as a drill) which is movable with use of any of thesecondary batteries as a power supply for drive. The electronic unitsare unit fulfilling various functions with use of any of the secondarybatteries as a power supply for drive.

Some application examples of the secondary batteries will be describedin detail below. It is to be noted that the configurations of theapplication examples which will be described below are just examples,and may be modified, as necessary.

(7-1. Battery Pack)

FIG. 7 illustrates a block configuration of a battery pack. Asillustrated in FIG. 7, the battery pack includes a control section 61, apower supply 62, a switch section 63, a current measurement section 64,a temperature detection section 65, a voltage detection section 66, aswitch control section 67, a memory 68, a temperature detection device69, a current sensing resistor 70, a cathode terminal 71, an anodeterminal 72 in an enclosure 60 made of a plastic material or the like.

The control section 61 controls operation of the entire battery pack(including a usage state of the power supply 62), and includes, forexample, a central processing unit (CPU). The power supply 62 includesone or two or more secondary batteries (not illustrated). The powersupply 62 is, for example, an assembled battery including two or moresecondary batteries, and the secondary batteries may be connected toeach other in series, in parallel, or in any series-parallelcombination. As an example, the power supply 62 includes six secondarybatteries connected in a configuration of two in parallel by three inseries.

The switch section 63 switches the usage state of the power supply 62(connection/disconnection between the power supply 62 and an externalunit) according to an instruction from the control section 61. Theswitch section 63 includes, for example, a charge control switch, adischarge control switch, a diode for charge, and a diode for discharge(all not illustrated). The charge control switch and the dischargecontrol switch are, for example, semiconductor switches such as metaloxide semiconductor field-effect transistors (MOSFETs) using a metaloxide semiconductor.

The current measurement section 64 measures a current with use of thecurrent sensing resistor 70, and outputs a measurement result to thecontrol section 61. The temperature detection section 65 measures atemperature with use of the temperature detection device 69, and outputsa measurement result to the control section 61. The temperaturemeasurement result is used, for example, in the case where the controlsection 61 performs charge-discharge control during abnormal heatgeneration or in the case where the control section 61 performs acorrection process during calculation of a capacity level. The voltagedetection section 66 measures the voltage of the secondary battery inthe power supply 62, and performs analog-digital (A/D) conversion on ameasured voltage to supply the voltage to the control section 61.

The switch control section 67 controls the operation of the switchsection 63 based on signals supplied from the current measurementsection 64 and the voltage detection section 66.

For example, when a battery voltage reaches an overcharge detectionvoltage, the switch control section 67 turns off the switch section 63(the charge control switch), thereby controlling a charge current not toflow through a current path of the power supply 62. Thus, in the powersupply 62, only discharge through the diode for discharge is allowed tobe executed. It is to be noted that, for example, when a large currentflows during charge, the switch control section 67 blocks a chargecurrent.

Moreover, for example, when the battery voltage reaches an overdischargedetection voltage, the switch control section 67 turns off the switchsection 63 (the discharge control switch), thereby controlling adischarge current not to flow through the current path of the powersupply 62. Thus, in the power supply 62, only charge through the diodefor charge is allowed to be executed. It is to be noted that, forexample, when a large current flows during discharge, the switch controlsection 67 blocks a discharge current.

It is to be noted that, in the secondary battery, for example, theovercharge detection voltage is 4.20 V±0.05 V, and the overdischargedetection voltage is 2.4 V±0.1 V.

The memory 68 is, for example, an EEPROM which is a non-volatile memory,or the like. In the memory 68, for example, values computed by thecontrol section 61, and information (for example, initial internalresistance) of the secondary battery measured in a manufacturing processare stored. It is to be noted that, when the value of full-chargecapacity of the secondary battery is stored in the memory 68, thecontrol section 61 is allowed to keep track of information such as thecapacity level.

The temperature detection device 69 measures the temperature of thepower supply 62, and outputs a measurement result to the control section61, and is, for example, a thermistor.

The cathode terminal 71 and the anode terminal 72 are terminalsconnected to an external unit (such as a notebook personal computer)operating by the battery pack or an external unit (such as a charger)used to charge the battery pack. The power supply 62 is charged anddischarged through the cathode terminal 71 and the anode terminal 72.

(7-2. Electric Vehicle)

FIG. 8 illustrates a block configuration of a hybrid vehicle as anexample of the electric vehicle. For example, as illustrated in FIG. 8,the electric vehicle includes a control section 74, an engine 75, apower supply 76, a drive motor 77, a differential gear 78, a generator79, a transmission 80 and a clutch 81, inverters 82 and 83, and varioussensors 84 in a body 73 made of metal. The electric vehicle furtherincludes, for example, a front-wheel axle 85 and front wheels 86 whichare connected to the differential gear 78 and the transmission 80, and arear-wheel axle 87 and rear wheels 88.

The electric vehicle is capable of running with use of one of the engine75 and the motor 77 as a driving source. The engine 75 is a main powersource, and is, for example, a gasoline engine or the like. When theengine 75 is used as a power source, for example, the driving force(torque) of the engine 75 is transmitted to the front wheels 86 or therear wheels 88 through drive sections, i.e., the differential gear 78,the transmission 80, and the clutch 81. It is to be noted that thetorque of the engine 75 is also transmitted to the generator 79, therebyallowing the generator 79 to generate AC power by the torque, and the ACpower is converted into DC power by the inverter 83 to be stored in thepower supply 76. On the other hand, in the case where the motor 77 as aconversion section is used as a power source, power (DC power) suppliedfrom the power supply 76 is converted into AC power by the inverter 82,and the motor 77 is driven by the AC power. For example, the drivingforce (torque) into which the power is converted by the motor 77 istransmitted to the front wheels 86 or the rear wheels 88 through thedrive sections, i.e., the differential gear 78, the transmission, andthe clutch 81.

It is to be noted that when the electric vehicle is slowed down by acontrol mechanism (not illustrated), resistance while slowing theelectric vehicle down may be transmitted to the motor 77 as a torque,thereby allowing the motor 77 to generate AC power by the torque. The ACpower is preferably converted into DC power by the inverter 82, therebystoring DC regenerative power in the power supply 76.

The control section 74 controls operation of the entire electricvehicle, and includes, for example, a CPU. The power supply 76 includesone or two or more secondary batteries (not illustrated). The powersupply 76 may be connected to an external power supply to receive powerfrom the external power supply; therefore, the power supply 76 isallowed to store power. The various sensors 84 are used to control theRPM of the engine 75 or opening of a throttle valve (throttle opening).The various sensors 84 include, for example, a speed sensor, anacceleration sensor, and an engine RPM sensor.

It is to be noted that the hybrid vehicle is described above as theelectric vehicle; however, the electric vehicle may be a vehicle(electric car) driven only by the power supply 76 and the motor 77without using the engine 75.

(7-3. Energy Storage System)

FIG. 9 illustrates a block configuration of an energy storage system.For example, as illustrated in FIG. 9, the energy storage systemincludes a control section 90, a power supply 91, a smart meter 92, anda power hub 93 in a house 89 such as a general house or a commercialbuilding.

In this case, for example, the power supply 91 is connected to anelectrical unit 94 placed in the house 89, and is connectable to anelectric vehicle 96 placed outside the house 89. Moreover, for example,the power supply 91 is connected to a private electric generator 95mounted on the house 89 through the power hub 93, and is connectable toan external centralized power system 97 through the smart meter 92 andthe power hub 93.

It is to be noted that examples of the electrical unit 94 include one ortwo or more household electrical appliances such as a refrigerator, anair conditioner, a television, and a boiler. Examples of the privateelectric generator 95 include one kind or two or more kinds of solarpower systems or wind power generators. Examples of the electric vehicle96 include one kind or two or more kinds of electric vehicles, electricmotorbikes, and hybrid vehicles. Examples of the centralized powersystem 97 include one kind or two or more kinds of thermal power plants,nuclear power plants, hydroelectric power plants, and wind power plants.

The control section 90 controls operation of the entire energy storagesystem including a usage state of the power supply 91), and includes,for example, a CPU. The power supply 91 includes one or two or moresecondary batteries (not illustrated). The smart meter 92 is anetwork-compatible wattmeter mounted in the house 89 demanding power,and is allowed to communicate with a power supplier. Accordingly, forexample, the smart meter 92 is allowed to control balance between demandand supply in the house 89 while communicating with an external unit asnecessary, thereby securing efficient and stable energy supply.

In the energy storage system, for example, power from the centralizedpower system 97 as the external power supply is stored in the powersupply 91 through the smart meter 92 and the power hub 93, and powerfrom the private electric generator 95 is stored in the power supply 91through the power hub 93. The power stored in the power supply 91 issupplied to the electrical unit 94 or the electric vehicle 96 asnecessary according to an instruction from the control section 91;therefore, the electrical unit 93 is allowed to operate, and theelectric vehicle 96 is allowed to be charged. In other words, the energystorage system is a system capable of storing and supplying power in thehouse with use of the power supply 91.

The power stored in the power supply 91 is arbitrarily usable.Therefore, for example, the power from the centralized power system 97is allowed to be stored in the power supply 91 at midnight at which apower rate is low, and the power stored in the power supply 91 isallowed to be used in the daytime in which the power rate is high.

It is to be noted that the above-described energy storage system may bemounted per house (per household), or per a plurality of houses (aplurality of households).

(7-4. Electric Power Tool)

FIG. 10 illustrates a block configuration of an electric power tool. Forexample, as illustrated in FIG. 10, the electric power tool is anelectric drill, and includes a control section 99 and a power supply 100in a tool body 98 formed of a plastic material. A drill section 101 as amovable section is operably (rotatably) attached to the tool body 98.

The control section 99 controls operation of the entire electric powertool (including a usage state of the power supply 100), and includes,for example, a CPU. The power supply 100 includes one or two or moresecondary batteries (not illustrated). The control section 99 allows thepower supply 100 to supply power to the drill section 101 as necessaryaccording to an operation of an operation switch (not illustrated),thereby bringing the drill section 101 into operation.

EXAMPLES

Examples of the technology will be described in detail below.

(1) Examples of First Embodiment

First, various characteristics of the secondary battery according to thefirst embodiment were determined.

Experimental Example 1-1 to 1-33

The prismatic type secondary batteries illustrated in FIGS. 1 and 2 wereformed by the following steps.

First, the cathode 21 was formed. Lithium carbonate (Li₂CO₃) and cobaltcarbonate (CoCO₃) were mixed at a mole ratio of 0.5:1 to form a mixture,and then the mixture was fired in air at 900° C. for 5 hours to obtainlithium cobalt complex oxide (LiCoO₂). Next, 91 parts by mass of thecathode active material (lithium cobalt complex oxide: LiCoO₂), 6 partsby mass of the cathode conductor (graphite) and 3 parts by mass of thecathode binder (polyvinylidene fluoride: PVDF) were mixed to form acathode mixture. Next, the cathode mixture was dispersed in the organicsolvent (N-methyl-2-pyrrolidone: NMP) to form paste-form cathode mixtureslurry. Then, the cathode mixture slurry was applied to both surfaces ofthe strip-like cathode current collector 21A (aluminum foil with athickness of 20 μm) by a coating unit, and the cathode mixture slurrywas dried to form the cathode active material layer 21B. Next, thecathode active material layer 21B was compression molded by a rollerpress.

Next, the anode 22 was formed. First, 90 parts by mass of the anodeactive material (artificial graphite) and 10 parts by mass of the anodebinder (PVDF) were mixed to form an anode mixture. Next, the anodemixture was dispersed in the organic solvent (NMP) to form paste-formanode mixture slurry. Then, the anode mixture slurry was applied to bothsurfaces of the strip-like anode current collector 22A (electrolyticcopper foil with a thickness of 15 μm) by a coating unit, and the anodemixture slurry was dried to form the anode active material layer 22B.Next, the anode active material layer 22B was compression molded by aroller press.

Next, the electrolyte salt was dissolved in the nonaqueous solvent, andthen the methylene cyclic carbonate represented by the expression (1)was added to the nonaqueous solvent to have one of compositionsillustrated in Tables 1 to 3 as necessary, thereby preparing theelectrolytic solution. In this case, a mixture of ethylene carbonate(EC) and ethyl methyl carbonate (EMC) was used as the nonaqueoussolvent, and the mixture ratio (weight ratio) of them was EC:EMC=50:50.As the electrolyte salt, lithium hexafluorophosphate (LiPF₆) was used,and the content of the electrolyte salt was 1 mol/kg relative to thesolvent. As the nonaqueous solvent, in addition to EC and EMC, propylenecarbonate (PC), diethyl carbonate (DEC) or dimethyl carbonate (DMC) wasused instead of EMC. Moreover, 4-fluoro-1,3-dioxolane-2-one (FEC) wasalso used.

Next, the secondary battery was assembled with use of the cathode 21,the anode 22, and the electrolytic solution. The cathode 21 and theanode 22 were laminated with the separator 23 (a microporouspolypropylene film with a thickness of 25 μm) in between, and werespirally wound to form a spirally wound body, and then the spirallywound body was molded into a flat shape to form the battery device 20.Next, the battery device 20 was contained in the battery can 11 made ofiron, and then the insulating plate 12 was put on the battery device 20.Next, the cathode lead 24 made of aluminum was welded to an end of thecathode current collector 21A, and the anode lead 25 made of nickel waswelded to the anode current collector 22A. In this case, the batterycover 13 was fixed to an open end of the battery can 11 by a laserwelding method. Finally, the electrolytic solution was injected into thebattery can 11 from the injection hole 19 to impregnate the separator 23with the electrolytic solution, and then the injection hole 19 wassealed with the sealing member 19A. Thus, the prismatic type secondarybattery was completed. When the secondary battery was formed, thethickness of the cathode active material layer 21B was adjusted toprevent lithium metal from being deposited on the anode 22 in afully-charged state.

It is to be noted that, instead of the prismatic type secondary battery,the cylindrical lithium-ion secondary batteries illustrated in FIGS. 5and 6 were also formed for comparison of battery configurations.

In this case, the spirally wound electrode body 40 was formed by stepssimilar to those of forming the above-described battery device 20,except that the spirally wound electrode body 40 was not molded in aflat shape, and then the cathode lead 45 was welded to the cathodecurrent collector 41A, and the anode lead 46 was welded to the anodecurrent collector 42A. Moreover, the center pin 44 was inserted into thecenter of the spirally wound electrode body 40. Next, the spirally woundelectrode body 40 sandwiched between the pair of insulating plates 32and 33 was contained in the battery can 31 made of nickel-plated iron.In this case, an end of the cathode lead 45 and an end of the anode lead46 were welded to the safety valve mechanism 35 and the battery can 31,respectively. Next, the electrolytic solution was injected into thebattery can 31 by a decompression method to impregnate the separator 43with the electrolytic solution. Finally, the battery cover 34, thesafety valve mechanism 35, and the PTC device 36 were caulked in an openend of the battery can 31 by the gasket 37. Thus, the cylindrical typesecondary battery was completed. Even in this secondary battery, thethickness of the cathode active material layer 41B was adjusted toprevent lithium metal from being deposited on the anode 42 in afully-charged state.

When initial charge-discharge characteristics and swellingcharacteristics of these secondary batteries were determined, resultsillustrated in Tables 1 to 3 were obtained.

To determine the initial charge-discharge characteristics, one cycle ofcharge and discharge was performed on each of the secondary batteries ina room temperature environment (at 23° C.) to stabilize its batterystate, and then each of the secondary batteries was charged again todetermine its charge capacity. Next, each of the secondary batteries wasdischarged to determine its discharge capacity. Initial efficiency(%)=(discharge capacity/charge capacity) 100 was determined from theseresults by calculation. As the conditions of charge, each of thesecondary batteries was charged at a constant current of 0.2 C and aconstant voltage until the voltage reached an upper-limit voltage of 4.2V, and then each of the secondary batteries was charged at a constantvoltage until the current reached 0.05 C. As the conditions ofdischarge, each of the secondary batteries was discharged at a constantcurrent of 0.2 C until the voltage reached a cutoff voltage of 2.5 V. Itis to be noted that “0.2 C” and “0.05 C” represent a current value atwhich the capacity (theoretical capacity) of a battery is fullydischarged for 5 hours and 20 hours, respectively.

To determine initial swelling characteristics, the thickness of each ofthe secondary batteries was measured in a room-temperature environment(at 23° C.). Next, one cycle of charge and discharge was performed inthe same environment to stabilize its battery state, and then each ofthe secondary batteries were charged again, and the thickness of each ofthe charged secondary batteries was measured. Initial swelling(mm)=thickness after charge and discharge−thickness before charge anddischarge was determined from these results by calculation. Theconditions of charge and discharge were similar to those in the casewhere the initial charge-discharge characteristics were determined.

To determine swelling characteristics during storage, one cycle ofcharge and discharge was performed on each of the secondary batteries ina room temperature environment (at 23° C.) to stabilize its batterystate, and then each of the secondary batteries was charged again, andthe thickness of each of the charged secondary batteries were measured.Next, each of the charged secondary batteries was stored for 12 hours ina constant temperature bath (at 85° C.), and then the thickness of eachof the charged secondary batteries was measured. Swelling during storage(mm)=thickness after storage−thickness before storage was determinedfrom these results by calculation. The conditions of charge anddischarge were similar to those in the case where the initialcharge-discharge characteristics were determined.

TABLE 1 Methylene Cyclic Carbonate Swelling Experimental BatteryElectrolyte Nonaqueous Content Initial Initial during ExampleConfiguration Salt Solvent Kind (wt %) Efficiency (%) Swelling (mm)Storage (mm) 1-1 Prismatic LiPF6 EC + EMC Expression 0.01 88.8 0.72 1.021-2 Type (1-1) 0.1 89.8 0.52 0.85 1-3 0.2 90.9 0.44 0.72 1-4 1 90.9 0.380.51 1-5 2 91.5 0.25 0.51 1-6 5 91.5 0.25 0.65 1-7 10 9.15 0.25 1.2 1-8EC + PC Expression 2 91.5 0.22 0.55 1-9 EC + DEC (1-1) 91.5 0.25 0.4 1-10 EC + DMC 91.5 0.25 0.81  1-11 EC + EMC Expression 2 91.5 0.28 0.52(1-2)  1-12 Expression 91.5 0.25 0.55 (1-4)  1-13 Expression 91.5 0.30.56 (1-5)  1-14 Expression 91.5 0.28 0.58 (1-28)  1-15 EC − EMC + FECExpression 2 91.7 0.25 0.41 (1-28)

TABLE 2 Methylene Cyclic Carbonate Swelling Experimental BatteryElectrolyte Nonaqueous Content Initial Initial during ExampleConfiguration Salt Solvent Kind (wt %) Efficiency (%) Swelling (mm)Storage (mm) 1-16 Prismatic LiPF6 EC + EMC Expression 0.01 89.5 0.65 1.11-17 Type (1-31) 0.1 90.2 0.47 0.92 1-18 0.2 91.5 0.38 0.8 1-19 1 91.70.3 0.62 1-20 2 92.5 0.22 0.62 1-21 5 92.5 0.22 0.74 1-22 10 92.5 0.221.35 1-23 EC + PC Expression 2 92.5 0.2 0.58 1-24 EC + DEC (1-31) 92.50.22 0.5 1-25 EC + DMC 92.5 0.22 0.91 1-26 EC + EMC + FEC 0.22 0.22 0.52

TABLE 3 Methylene Cyclic Carbonate Swelling Experimental BatteryElectrolyte Nonaqueous Content Initial Initial during ExampleConfiguration Salt Solvent Kind (wt %) Efficiency (%) Swelling (mm)Storage (mm) 1-27 Prismatic LiPF6 EC + EMC — — 88.1 1.22 1.52 1-28 TypeEC + PC 21.0 9.25 unmeasurable 1-29 EC − DEC 89.8 0.99 1.02 1-30 EC −DMC 88.2 1.53 2.51 1-31 EC − EMC + FEC 90.2 0.63 1.01 1-32 CylindricalLiPF6 EC + EMC — — 91.3 0 0 1-33 Type Expression 2 91.3 0 0 (1-1)

In the prismatic type secondary batteries, when the electrolyticsolution included the methylene cyclic carbonate, high initialefficiency was obtained, and initial swelling and swelling duringstorage were kept low.

More specifically, there was no difference in the initial efficiency,the initial swelling, and swelling during storage between thecylindrical type secondary batteries (Experimental Examples 1-32 and1-33) irrespective of whether the electrolytic solution included themethylene cyclic carbonate. On the other hand, in the prismatic typesecondary batteries (Experimental Examples 1-1 to 1-31), in the casewhere the electrolytic solution included the methylene cyclic carbonate,compared to the case where the electrolytic solution did not include themethylene cyclic carbonate, the initial efficiency was increased, andthe initial swelling and swelling during storage were reduced. In thiscase, in particular, when the content of the methylene cyclic carbonatein the electrolytic solution was within a range of 0.01 wt % to 10 wt %both inclusive, more specifically within a range of 0.1 wt % to 5 wt %both inclusive, better results were obtained.

(2) Examples of Second Embodiment

Next, various characteristics of the secondary battery according to thesecond embodiment were determined.

Experimental Examples 2-1 to 2-36

The prismatic type lithium-ion secondary batteries were formed by stepssimilar to those in the examples of the first embodiment, except thatthe composition of the electrolytic solution was different from that inthe examples of the first embodiment. The electrolytic solution wasprepared by dissolving the electrolyte salt (LiPF₆) in the nonaqueoussolvent (EC and DMC), and then adding the methylene cyclic carbonaterepresented by the expression (11) and the auxiliary compound to thenonaqueous solvent as necessary, thereby allowing the electrolyticsolution to have one of compositions illustrated in Tables 4 to 6. Inthis case, as the composition of the nonaqueous solvent, the weightratio was EC:DMC=50:50, and the content of the electrolyte salt was 1mol/kg relative to the nonaqueous solvent.

When cycle characteristics and storage characteristics of thesesecondary batteries were determined, results illustrated in Tables 4 to6 were obtained.

To determine the cycle characteristics, one cycle of charge anddischarge was performed on each of the secondary batteries in aroom-temperature environment (at 23° C.) to stabilize its battery state,and then another cycle of charge and discharge was performed on each ofthe secondary batteries in a high-temperature environment (at 60° C.) todetermine the discharge capacity of each of the secondary batteries.Next, the cycle of charge and discharge in the same environment wasrepeated until the total cycle number reached 100 cycles to determinethe discharge capacity of each of the secondary batteries. A cycleretention ratio (%)=(discharge capacity in the 100th cycle/dischargecapacity in the second cycle)×100 was determined from these results bycalculation. The conditions of charge and discharge were similar tothose in the examples of the first embodiment.

To determine the storage characteristics, one cycle of charge anddischarge was performed, in a room temperature environment (at 23° C.),on each of the secondary batteries of which the battery states werestabilized by steps similar to those in the case where the cyclecharacteristics were determined to determine the discharge capacity ofeach of the secondary batteries. Next, each of the secondary batterieswas charged again, and each of the charged secondary batteries wasstored for 10 days in a constant temperature bath (at 80° C.), and theneach of the secondary batteries was discharged in a room-temperatureenvironment (at 23° C.) to determine its discharge capacity. A storageretention ratio (%)=(discharge capacity after storage/discharge capacitybefore storage)×100 was determined from these results by calculation.The conditions of charge and discharge were similar to those in theexamples of the first embodiment.

TABLE 4 Methylene Cyclic Carbonate Auxiliary Compound Cycle StorageExperimental Electrolyte Nonaqueous Content Content Retention RetentionExample Salt Solvent Kind (wt %) Kind (wt %) Ratio (%) Ratio (%) 2-1LiPF6 EC + DMC Expression 2 LiPF2O2 0.001 81 88 2-2 (1-1) 0.1 83 89 0.286 0.290 2-4 1 83 88 2-5 2 81 88 2-6 Expression 0.01 LiPF2O2 0.2 80 862-7 (1-1) 0.5 82 87 2-8 1 86 88 2-9 5 86 90  2-10 10 82 88  2-11Expression 2 Expression 0.2 84 89 (1-1) (12-45)  2-12 Expression 0.2 8690 (13-1)  2-13 Expression 0.2 83 88 (14-1)  2-14 Li2PFO3 0.2 85 90

TABLE 5 Methylene Cyclic Carbonate Auxiliary Compound Cycle StorageExperimental Electrolyte Nonaqueous Content Content Retention RetentionExample Salt Solvent Kind (wt %) Kind (wt %) Ratio (%) Ratio (%) 2-15LiPF6 EC + DMC Expression 2 LiPF2O2 0.001 83 90 2-16 (1-31) 0.1 85 912-17 0.2 88 92 2-18 1 86 90 2-19 2 84 90 2-20 Expression 0.01 LiPF2O20.2 82 88 2-21 (1-31) 0.5 84 90 2-22 1 88 92 2-23 5 88 90 2-24 10 84 892-25 Expression 2 Expression 0.2 88 91 (1-31) (12-45) 2-26 Expression0.2 90 92 (13-1) 2-27 Expression 0.2 87 90 (14-1) 2-28 Li2PFO3 0.2 86 92

TABLE 6 Methylene Cyclic Carbonate Auxiliary Compound Cycle StorageExperimental Electrolyte Nonaqueous Content Content Retention RetentionExample Salt Solvent Kind (wt %) Kind (wt %) Ratio (%) Ratio (%) 2-29LiPF6 EC + DMC — — — — 75 81 2-30 Expression 2 — — 77 80 (1-1) 2-31Expression 2 — — 76 80 (1-31) 2-32 — — Expression 0.2 77 82 (12-45) 2-33Expression 0.2 76 82 (13-1) 2-34 Expression 0.2 78 81 (14-1) 2-35Li2PFO3 0.2 77 82 2-36 LiPF2O2 0.2 78 82

When the electrolytic solution included the methylene cyclic carbonateand the auxiliary compound, a high cycle retention ratio and a highstorage retention ratio were obtained.

More specifically, with reference to the case where the methylene cycliccarbonate and the auxiliary compound were not used (Experimental Example2-29), in the case where only the methylene cyclic carbonate was used(Experimental Examples 2-30 and 2-31), the storage retention ratio wasslightly increased, but the cycle retention ratio was reduced, and inthe case where only the auxiliary compound was used (ExperimentalExamples 2-32 to 2-36), the cycle retention ratio and the storageretention ratio were only slightly increased. On the other hand, in thecase where the methylene cyclic carbonate and the auxiliary compoundwere used (Experimental Example 2-1 to 2-28), the cycle retention ratioand the storage retention ratio were both increased, and in particular,the storage retention ratio was remarkably increased. This resultindicates that when the electrolytic solution includes the methylenecyclic carbonate and the auxiliary compound, decomposition reaction ofthe electrolytic solution is specifically suppressed even in ahigh-temperature environment.

In particular, in the case where the methylene cyclic carbonate and theauxiliary compound were used, when the content of the methylene cycliccarbonate in the electrolytic solution was within a range of 0.01 wt %to 10 wt % both inclusive, more specifically within a range of 0.5 wt %to 5 wt % both inclusive, better results were obtained. Likewise, whenthe content of the auxiliary compound in the electrolytic solution waswithin a range of 0.001 wt % to 2 wt % both inclusive, more specificallywithin a range of 0.1 wt % to 1 wt % both inclusive, better results wereobtained.

Experimental Examples 3-1 to 3-18

Secondary batteries were formed by steps similar to those inExperimental Example 2-3, except that the composition of the nonaqueoussolvent was changed as illustrated in Table 7, and variouscharacteristics of the secondary batteries were determined. As thecomposition of the nonaqueous solvent, the weight ratio wasEC:PC:DMC=10:20:70. The content of vinylene carbonate (VC) in thenonaqueous solvent was 2 wt %, and the content of FEC,trans-4,5-difluoro-1,3-dioxolane-2-one (t-DFEC), orbis(fluoromethyl)carbonate (DFDMC) in the nonaqueous solvent was 5 wt %.

TABLE 7 Methylene Cyclic Carbonate Auxiliary Compound Cycle StorageExperimental Electrolyte Nonaqueous Content Content Retention RetentionExample Salt Solvent Kind (wt %) Kind (wt %) Ratio (%) Ratio (%) 3-1 LiPF EC + DEC Expression 2 LiPF2O2 0.2 81 90 3-2  EC + EMC (1-1) 82 903-3  EC + PC + DMC 86 90 3-4  EC + DMC VC 90 92 3-5  FEC 90 90 3-6 t-DFEC 89 90 3-7  DFDMC 89 88 3-8  LiPF6 EC + DEC Expression 2 LiPF2O20.2 89 92 3-9  EC + EMC (1-31) 89 92 3-10 EC + PC + DMC 89 92 3-11 EC +DMC VC 92 94 3-12 FEC 94 94 3-13 t-DFEC 92 93 3-14 DFDMC 92 93 3-15LiPF6 EC + DMC VC — — — — 80 83 3-16 FEC 79 84 3-17 t-DFEC 79 84 3-18DFDMC 78 82

Even though the composition of the nonaqueous solvent was changed, ahigh cycle retention ratio and a high storage retention ratio wereobtained. In particular, when the electrolytic solution included anunsaturated cyclic carbonate, a halogenated cyclic carbonate, or ahalogenated chain carbonate, the cycle retention ratio and the storageretention ratio were increased.

Experimental Examples 4-1 to 4-3

Secondary batteries were formed by steps similar to those inExperimental Example 2-3, except that the composition of the electrolytesalt was changed as illustrated in Table 8, and various characteristicsof the secondary batteries were determined. As the electrolyte salt,lithium tetrafluoroborate (LiBF4), (4,4,4-trifluorobutyrate oxalato)lithium borate (LiTFOB) represented by the expression (7-8), or lithiumbis(trifluoromethane-sulfonyl)imide (LiN(CF₃SO₂)₂: LiTFSI) was used. Inthis case, the content of LiPF₆ was 0.9 mol/kg relative to thenonaqueous solvent, and the content of LiBF₄ or the like was 0.1 mol/kgrelative to the nonaqueous solvent.

TABLE 8 Methylene Cyclic Carbonate Auxiliary Compound Cycle StorageExperimental Electrolyte Nonaqueous Content Content Retention RetentionExample Salt Solvent Kind (wt %) Kind (wt %) Ratio (%) Ratio (%) 4-1LiPF6 LiBF4 EC + DMC Expression 2 LiPF2O2 0.2 85 92 4-2 LiTFOB (1-1) 8693 4-3 LiTFSI 88 92

Even though the composition of the electrolyte salt was changed, a highcycle retention ratio and a high storage retention ratio were obtained.In particular, when the electrolytic solution included other electrolytesalt such as LiBF₄, the cycle retention ratio and the storage retentionratio were further increased.

(3) Examples of Third Embodiment

Next, various characteristics of the secondary battery according to thethird embodiment were determined.

Experimental Examples 5-1 to 5-36

Prismatic type lithium-ion secondary batteries were formed by stepssimilar to those in the examples of the first embodiment, except thatthe composition of the electrolytic solution was different from that inthe examples of the first embodiment. The electrolytic solution wasprepared by dissolving the electrolyte salt (LiPF₆) in the nonaqueoussolvent (EC and DMC), and then adding the methylene cyclic carbonaterepresented by the expression (17) and a halogenated carbonate or thelike as necessary, thereby allowing the electrolytic solution to haveone of compositions illustrated in Tables 9 to 11. As the composition ofthe nonaqueous solvent, the weight ratio was EC:DMC=50:50, and thecontent of the electrolyte salt was 1 mol/kg relative to the nonaqueoussolvent, and the content of VC in the electrolytic solution was 1 wt %.

When cycle characteristics and storage characteristics of the secondarybatteries were determined by steps similar to those in the examples ofthe second embodiment, results illustrated in Tables 9 to 11 wereobtained.

TABLE 9 Methylene Cyclic Halogenated Carbonate Carbonate Cycle StorageExperimental Electrolyte Nonaqueous Content Content Retention RetentionExample Salt Solvent Kind (wt %) Kind (wt %) Ratio (%) Ratio (%) 5-1LiPF6 EC + DMC Expression 0.01 FEC 5 80 85 5-2 (1- 0.1 82 87 5-3 0.5 8588 5-4 1 85 89 5-5 2 86 90 5-6 5 86 90 5-7 10 85 89 5-8 Expression 2 FEC0.1 79 82 5-9 (1-1) 0.5 80 84  5-10 1 81 86  5-11 10 90 90  5-12 20 9089  5-13 LiPF6 EC + DMC Expression 2 t-DFEC 5 84 88  5-14 (1-1) DFDMC 8589  5-15 EC + DMC VC Expression 2 FEC 5 92 94 (1-1)

TABLE 10 Methylene Cyclic Halogenated Carbonate Carbonate Cycle StorageExperimental Electrolyte Content Content Retention Retention ExampleSalt Solvent Kind (wt %) Kind (wt %) Ratio (%) Ratio (%) 5-16 LiPF6 EC +DMC Expression 0.01 FEC 5 82 88 5-17 (1-31) 0.1 84 90 5-18 0.5 86 925-19 1 86 92 5-20 2 87 93 5-21 5 87 93 5-22 10 86 90 5-23 Expression 2FEC 0.1 81 84 5-24 (1-31) 0.5 83 87 5-25 1 85 90 5-26 10 92 92 5-27 2092 90 5-28 LiPF6 EC + DMC Expression 2 t-DFEC 5 86 90 5-29 5-2 (1-31)DFDMC 86 90 5-30 EC + DMC VC Expression 2 FEC 5 90 90 (1-31)

TABLE 11 Methylene Cyclic Halogenated Carbonate Carbonate Cycle StorageExperimental Electrolyte Nonaqueous Content Content Retention RetentionExample Salt Solvent Kind (wt %) Kind (wt %) Ratio (%) Ratio (%) 5-31LiPF6 EC + DMC — — — — 75 81 5-32 Expression 2 — — 77 80 (1-1) 5-33 — —FEC 5 79 84 5-34 t-DFEC 79 84 5-35 DFDMC 78 82 5-36 EC + DMC VC — — — —80 83

When the electrolytic solution included the methylene cyclic carbonateand the halogenated carbonate, a high cycle retention ratio and a highstorage retention ratio were obtained.

More specifically, with reference to the case where the methylene cycliccarbonate and the halogenated carbonate were not included (ExperimentalExample 5-31), in the case where only the methylene cyclic carbonate wasused (Experimental Example 5-32), the cycle retention ratio was slightlyincreased, but the storage retention ratio was reduced, and in the casewhere only the halogenated carbonate was used (Experimental Examples5-33 to 5-35), the cycle retention ratio and the storage retention ratiowere only slightly increased. On the other hand, in the case where themethylene cyclic carbonate and the halogenated carbonate were used(Experimental Examples 5-1 to 5-30), the cycle retention ratio and thestorage retention ratio were remarkably increased. The increased amountfar exceeded an increased amount expected from results obtained in thecase where only one of methylene cyclic carbonate and halogenatedcarbonate was used. In other words, this result indicates that when theelectrolytic solution includes the methylene cyclic carbonate and thehalogenated carbonate, decomposition reaction of the electrolyticsolution is specifically suppressed even in a high-temperatureenvironment by a synergistic interaction between the methylene cycliccarbonate and the halogenated carbonate.

In particular, in the case where the methylene cyclic carbonate and thehalogenated carbonate were used, when the content of the methylenecyclic carbonate in the electrolytic solution was within a range of 0.01wt % to 10 wt % both inclusive, more specifically within a range of 0.1wt % to 5 wt % both inclusive, better results were obtained. Likewise,when the content of the halogenated carbonate in the electrolyticsolution was within a range of 0.1 wt % to 20 wt % both inclusive, morespecifically within a range of 5 wt % to 20 wt % both inclusive, betterresults were obtained. Moreover, when the electrolytic solution includedthe unsaturated cyclic carbonate, the cycle retention ratio and thestorage retention ratio were further increased.

(4) Examples of Fourth Embodiment

Next, various characteristics of the secondary battery according to thefourth embodiment were determined.

Experimental Examples 6-1 to 6-21

Prismatic lithium-ion secondary batteries were formed by steps similarto those in the examples of the first embodiment, except that thecomposition of the electrolytic solution was different from that in theexamples of the first embodiment. The electrolytic solution was preparedby dissolving the electrolyte salt (LiPF₆) in the nonaqueous solvent (ECand DMC), and then adding one of the methylene cyclic carbonatesrepresented by the expressions (20) to (22) and the auxiliary compoundas necessary, thereby allowing the electrolytic solution to have one ofcompositions illustrated in Table 12. As the composition of thenonaqueous solvent, the weight ratio was EC:DMC=50:50, and the contentof the electrolyte salt was 1 mol/kg relative to the nonaqueous solvent.

When initial charge-discharge characteristics of the secondary batterieswere determined by steps similar to those in the examples of the firstembodiment, and cycle characteristics and storage characteristics of thesecondary batteries were determined by steps similar to those in theexamples of the second embodiment, results illustrated in Table 12 wereobtained.

TABLE 12 Methylene Cyclic Auxiliary Carbonate Compound Cycle StorageExperimental Electrolyte Nonaqueous Content Content Initial RetentionRetention Example Salt Solvent Kind (wt %) Kind (wt %) Efficiency (%)Ratio (%) Ratio (%) 6-1  LiPF6 EC + DMC Expression 0.01 — — 91.5 77 846-2  (1-4) 0.1 91.7 78 85 6-3  0.5 91.8 78 86 6-4  1 92.0 80 87 6-5  292.2 82 87 6-6  5 92.2 82 86 6-7  10 92.0 80 84 6-8  Expression 2 92.081 85 (1-5) 6-9  Expression 92.0 80 85 (1-10) 6-10 Expression 91.8 81 84(1-12) 6-11 Expression 92.0 81 85 (1-13) 6-12 Expression 91.9 81 84(1-28) 6-13 Expression 91.8 81 84 (1-29) 6-14 Expression 2 Expression0.2 — 86 90 (1-4) (12-45) 6-15 Expression 0.2 — 88 92 (13-1) 6-16Expression 0.2 — 84 91 (14-1) 6-17 Li2PFO3 0.2 — 86 91 6-18 LiPF2O2 0.2— 87 92 6-19 LiPF6 EC + DMC — — — — 91.3 75 81 6-20 Expression 2 91.3 7780 (1-1) 6-21 Expression 2 91.3 77 80 (1-7)

When the electrolytic solution included the methylene cyclic carbonatewith a specific structure, a high cycle retention ratio and a highstorage retention ratio were obtained.

More specifically, with reference to the case where the methylene cycliccarbonate was not used (Experimental Example 6-19), in the case wherethe methylene cyclic carbonate did not satisfy conditions represented bythe expressions (20) to (22) (Experimental Examples 6-20 and 6-21), thecycle retention ratio was slightly increased, but the storage retentionratio was reduced. On the other hand, in the case where the methylenecyclic carbonate satisfied the conditions represented by the expressions(20) to (22) (Experimental Examples 6-1 to 6-18), compared to theabovedescribed reference case, the cycle retention ratio and the storageretention ratio were both increased. This result indicates that when theelectrolytic solution includes the methylene cyclic carbonate with aspecific structure, decomposition reaction of the electrolytic solutionis specifically suppressed even in a high-temperature environment.

In particular, in the case where the methylene cyclic carbonate wasused, the content of the methylene cyclic carbonate in the electrolyticsolution was within a range of 0.01 wt % to 10 wt % both inclusive,better results were obtained. Moreover, when the electrolytic solutionincluded the auxiliary compound, the cycle retention ratio and thestorage retention ratio were further increased.

(5) Examples of Fifth Embodiment

Next, various characteristics of the secondary battery according to thefifth embodiment were determined.

Experimental Examples 7-1 to 7-25, 8-1 to 8-25

Secondary batteries were formed by steps similar to those inExperimental Examples 1-1 to 1-7, except that the composition of theelectrolytic solution was changed as illustrated in Tables 13 and 14,and various characteristics of the secondary batteries were determined.In this case, the content A (wt %) of the unsaturated cyclic carbonate(the vinylene carbonate-based compound), the content B (wt %) of themethylene cyclic carbonate, the ratio B/A were changed. As theunsaturated cyclic carbonate, methyl vinylene carbonate (MVC) and VCwere used.

In this case, in addition to the cycle characteristics and the storagecharacteristics, load characteristics were determined. To determine theload characteristics, one cycle of charge and discharge was performed,in a room temperature environment (at 23° C.), on each of the secondarybatteries of which the battery state is stabilized by steps similar tothose in the case where the cycle characteristics were determined todetermine the discharge capacity of each of the secondary batteries.Next, the cycle of charge and discharge in a low-temperature environment(−10° C.) was repeated until the total cycle number reached 100 cyclesto determine the discharge capacity of each of the secondary batteries.A load retention ratio (%)=(discharge capacity in the 100thcycle/discharge capacity in the second cycle)×100 was determined fromthese results by calculation. The conditions of charge were similar tothose in the case where the cycle characteristics were determined. Asthe conditions of discharge, each of the secondary batteries wasdischarged at a constant current of 1 C until the voltage reached acutoff voltage of 2.5 V. It is to be noted that “1 C” represents acurrent value at which the capacity (theoretical capacity) of a batteryis fully discharged for 1 hour.

TABLE 13 Unsaturated Cyclic Carbonate Methylene Cyclic Carbonate CycleStorage Load Experimental Content A Content B Retention RetentionRetention Example Kind (wt %) Kind (wt %) Ratio B/A Ratio (Vo) Ratio (%)Ratio (%) 7-1  MVC 10 Expression 0.01 0.001 80 84 30 7-2  5 (1-1) 0.00285 85 52 7-3  1 0.01 82 87 58 7-4  0.01 1 80 82 55 7-5  0.001 10 77 8142 7-6  MVC 10 Expression 0.1 0.01 82 84 30 7-7  5 (1-1) 0.02 85 85 547-8  1 0.1 84 87 65 7-9  0.01 10 83 84 60 7-10 0.001 100 78 82 45 7-11MVC 10 Expression 3 0.3 84 85 30 7-12 5 (1-1) 0.6 85 86 60 7-13 1 3 8890 67 7-14 0.01 300 85 89 66 7-15 0.001 3000 82 88 40 7-16 MVC 10Expression 5 0.5 83 83 20 7-17 5 (1-1) 1 85 84 50 7-18 1 5 86 86 55 7-190.01 500 84 85 48 7-20 0.001 5000 80 83 38 7-21 MVC 10 Expression 10 180 82 15 7-22 5 (1-1) 2 82 82 23 7-23 1 10 84 84 25 7-24 0.01 1000 82 8220 7-25 0.001 10000 78 82 10

TABLE 14 Unsaturated Cyclic Carbonate Methylene Cyclic Carbonate CycleStorage Load Content A Content B Retention Retention Retention ExampleKind (wt %) Kind (wt %) Ratio B/A Ratio (%) Ratio (%) Ratio (%) 8-1  VC10 Expression 0.01 0.001 82 85 30 8-2  5 (1-1) 0.002 84 85 50 8-3  10.01 82 87 55 8-4  0.01 1 78 82 33 8-5  0.001 10 77 81 40 8-6  VC 10Expression 0.1 0.01 82 85 30 8-7  5 (1-1) 0.02 85 85 52 8-8  1 0.1 84 8860 8-9  0.01 10 80 84 55 8-10 0.001 100 78 82 40 8-11 VC 10 Expression 30.3 84 85 30 8-12 5 (1-1) 0.6 86 86 55 8-13 1 3 88 90 65 8-14 0.01 30084 89 65 8-15 0.001 3000 82 88 40 8-16 VC 10 Expression 5 0.5 83 83 208-17 5 (1-1) 1 85 84 45 8-18 1 5 86 86 50 8-19 0.01 500 82 85 48 8-200.001 5000 80 83 38 8-21 VC 10 Expression 10 1 80 82 15 8-22 5 (1-1) 282 82 23 8-23 1 10 84 84 25 8-24 0.01 1000 78 82 20 8-25 0.001 10000 7882 10

Even though the ratio B/A was changed, a high cycle retention ratio anda high storage retention ratio were obtained when the electrolyticsolution included the methylene cyclic carbonate. In particular, whenthree conditions: that A be equal to 0.01 wt % to 5 wt % both inclusive;that B be equal to 0.01 wt % to 5 wt % both inclusive; and that theratio B/A be equal to 0.002 to 500 both inclusive were concurrentlysatisfied, a high load retention ratio was obtained.

It is to be noted that, even in the case where the electrolytic solutionincludes the unsaturated cyclic carbonate in the secondary batteriesaccording to the first to fourth embodiments, when the contents A and Band the ratio B/A are appropriately adjusted in a similar manner as thatin the fifth embodiment, similar results as those in Tables 13 and 14are supposed to be obtained.

When the composition of the nonaqueous solvent in the secondary batteryaccording to the first embodiment as a representative of theabove-described secondary batteries according to the first to fifthembodiments was appropriately adjusted, the following results wereobtained.

Experimental Examples 9-1 to 9-30

Secondary batteries were formed by steps similar to those inExperimental Examples 1-1 to 1-7, except that the composition of theelectrolytic solution was changed as illustrated in Tables 15 and 16,and various characteristics of the secondary batteries were determined.In this case, the content C (wt %) of the halogenated carbonate, thecontent D (wt %) of the methylene cyclic carbonate, and the ratio D/Cwere changed. As the halogenated carbonate, FEC was used.

TABLE 15 Halogenated Methylene Cyclic Carbonate Carbonate Cycle StorageLoad Experimental Content C Content D Retention Retention RetentionExample Kind (wt %) Kind (wt %) Ratio D/C Ratio (%) Ratio (%) Ratio (%)9-1  FEC 40 Expression 0.01 0.00025 90 81 30 9-2  30 (1-1) 1/3000 90 8245 9-3  5 0.002 80 85 55 9-4  1 0.01 79 85 55 9-5  0.01 1 78 82 44 9-6 0.001 10 77 81 40 9-7  FEC 40 Expression 0.1 0.0025 92 81 30 9-8  30(1-1) 1/300  91 83 48 9-9  5 0.02 82 87 58 9-10 1 0.1 80 86 58 9-11 0.0110 79 82 46 9-12 0.001 100 78 81 40 9-13 FEC 40 Expression 3 0.075 92 8230 9-14 30 (1-1) 0.1 92 85 50 9-15 5 0.6 86 90 60 9-16 1 3 81 86 60 9-170.01 300 79 83 48 9-18 0.001 3000 78 82 40

TABLE 16 Halogenated Methylene Cyclic Carbonate Carbonate Cycle StorageLoad Experimental Content C Content D Retention Retention RetentionExample Kind (wt %) Kind (wt %) Ratio D/C Ratio (%) Ratio (%) Ratio (%)9-19 FEC 40 Expression 5 0.125 90 82 20 9-20 30 (1-1) 1/6 89 84 42 9-215 1 86 90 50 9-22 1 5 80 85 50 9-23 0.01 500 79 82 44 9-24 0.001 5000 7882 40 9-25 FEC 40 Expression 10 0.25 88 82 15 9-26 30 (1-1) 1/3 88 84 209-27 5 2 85 89 32 9-28 1 10 80 84 32 9-29 0.01 1000 78 82 24 9-30 0.00110000 78 82 10

Even though the ratio D/C was changed, a high cycle retention ratio anda high storage retention ratio were obtained when the electrolyticsolution included the methylene cyclic carbonate. In particular, whenthree conditions: that C be equal to 0.01 wt % to 30 wt % bothinclusive; that D be equal to 0.01 wt % to 5 wt % both inclusive; andthat the ratio D/C be equal to 1/3000 to 500 both inclusive wereconcurrently satisfied, a high load retention ratio was obtained.

Experimental Examples 10-1 to 10-42

Secondary batteries were formed by steps similar to those inExperimental Examples 1-1 to 1-7, except that the mixture ratio ofcyclic carbonates EC and PC was changed as illustrated in Tables 17 and18, and various characteristics of the secondary batteries weredetermined. It is to be noted that “unmeasurable” in the tablesindicates that the discharge capacity and the thickness were notmeasured due to breakage of the secondary battery or the like.

TABLE 17 Cyclic Methylene Cyclic Carbonate Carbonate Initial SwellingLoad Experimental Mixture Ratio Content Initial Swelling duringRetention Example Kind (Weight Ratio) Kind (wt %) Efficiency (%) mm (%)Storage (mm) Ratio (%) 10-1  EC:PC 90:10 Expression 0.01 89.5 0.55 0.5230 10-2  75:25 (1-1) 89 0.6 0.43 45 10-3  50:50 88.4 0.85 0.4 50 10-4 40:60 88 0.98 0.33 53 10-5  25:75 86 1.2 0.2 40 10-6   0:100 82 2.820.18 20 10-7  EC:PC 90:10 Expression 0.1 91 0.25 0.52 32 10-8  75:25(1-1) 90.5 0.3 0.45 48 10-9  50:50 90.2 0.35 0.42 53 10-10 40:60 90 0.460.36 58 10-11 25:75 89.5 0.5 0.22 50 10-12  0:100 86 1.22 0.18 30 10-13EC:PC 90:10 Expression 1 91.7 0.2 0.62 30 10-14 75:25 (1-1) 91.5 0.220.55 50 10-15 50:50 91.3 0.22 0.5 64 10-16 40:60 91.3 0.22 0.4 62 10-1725:75 91.3 0.22 0.17 45 10-18  0:100 89.3 0.52 0.15 32 10-19 EC:PC 90:10Expression 3 92 0.2 0.65 28 10-20 75:25 (1-1) 91.7 0.22 0.6 45 10-2150:50 91.5 0.22 0.55 55 10-22 40:60 91.5 0.22 0.45 52 10-23 25:75 91.50.22 0.2 43 10-24  0:100 91 0.24 0.18 25

TABLE 18 Cyclic Methylene Cyclic Carbonate Carbonate Initial SwellingLoad Experimental Mixture Ratio Content Initial Swelling DuringRetention Example Kind (Weight Ratio) Kind (wt %) Efficiency (%) (mm)Storage (mm) Ratio (%) 10-25 EC:PC 90:10 Expression 5 92 0.2 0.75 3010-26 75:25 (1-1) 92 0.2 0.7 42 10-27 50:50 92 0.2 0.62 50 10-28 40:6092 0.2 0.5 48 10-29 25:75 92 0.2 0.44 45 10-30  0:100 92 0.2 0.36 2010-31 EC:PC 90:10 Expression 10 92 0.2 0.95 15 10-32 75:25 (1-1) 92 0.20.88 30 10-33 50:50 92 0.2 0.72 45 10-34 40:60 92 0.2 0.62 40 10-3525:75 92 0.2 0.55 38 10-36  0:100 92 0.2 0.5 20 10-37 EC:PC 90:10 — —42.3 6.72 unmeasurable 25 10-38 75:25 30.5 7.52 unmeasurable 30 10-3950:50 21 9.25 unmeasurable 35 10-40 40:60 unmeasurable unmeasurableunmeasurable unmeasurable 10-41 25:75 unmeasurable unmeasurableunmeasurable unmeasurable 10-42  0:100 unmeasurable unmeasurableunmeasurable unmeasurable

Even though the mixture ratio of EC and PC was changed, high initialefficiency was obtained, and initial swelling and swelling duringstorage were kept low when the electrolytic solution included themethylene cyclic carbonate. In particular, when two conditions: that themixture ratio EC:PC be equal to 75:25 to 25:75 both inclusive; and thatthe content of the methylene cyclic carbonate be equal to 0.01 wt % to10 wt % both inclusive were concurrently satisfied, a high loadretention ratio was obtained.

It is to be noted that, even in the case where the electrolytic solutionincludes the halogenated carbonate in the secondary batteries accordingto the second to fifth embodiments, when the contents C and D and theratio D/C are appropriately adjusted in the above-described manner,similar results as those in Tables 15 and 16 are supposed to beobtained. Moreover, even in the case where the electrolytic solutionincludes both of EC and PC in the secondary batteries according to thesecond to fifth embodiments, when the mixture ratio of EC and PC and thecontent of the methylene cyclic carbonate are appropriately adjusted inthe above-described manner, similar results as those in Tables 17 and 18are supposed to be obtained.

The following are found out from the results in Tables 1 to 18. In thistechnology, firstly, in the secondary battery using a package memberwith a flat external surface, when the electrolytic solution includesthe methylene cyclic carbonate represented by the expression (1),initial charge-discharge characteristics and swelling characteristicsare improved, thereby obtaining good battery characteristics. Secondly,when the electrolytic solution includes the methylene cyclic carbonaterepresented by the expression (11) and the auxiliary compound, the cyclecharacteristics and the storage characteristics are improved, therebyobtaining good battery characteristics. Thirdly, when the electrolyticsolution includes the methylene cyclic carbonate represented by theexpression (17) and the halogenated carbonate, cycle characteristics andstorage characteristics are improved, thereby obtaining good batterycharacteristics. Fourthly, when the electrolytic solution includes themethylene cyclic carbonates represented by the expressions (20) to (22),initial charge-discharge characteristics, cycle characteristics, andstorage characteristics are improved, thereby obtaining good batterycharacteristics. Moreover, the above-described results are obtainablewithout relying on the composition of the nonaqueous solvent, thecomposition of the electrolytic salt, or the like.

Although the present application is described referring to theembodiments and the examples, the technology is not limited thereto, andmay be variously modified. For example, as the kind of secondarybattery, the lithium-ion secondary battery and the lithium metalsecondary battery are described; however, the technology is not limitedthereto. The technology is also applicable to a secondary battery inwhich the capacity of an anode includes a capacity by insertion andextraction of lithium ions and a capacity associated with deposition anddissolution of lithium metal and its battery capacity is represented bythe sum of them. In this case, an anode material capable of insertingand extracting lithium ions is used, and a chargeable capacity of theanode material is set to be smaller than the discharge capacity of acathode.

Moreover, in the embodiments and the examples, the case where thebattery configuration is the prismatic type, the cylindrical type, orthe laminate film type, and the case where the battery device has aspirally wound configuration are described; however, the technology isnot limited thereto. The technology is also applicable, in a similarmanner, to the case where the secondary battery has any other batteryconfiguration such as a coin type, or a button type, or the case wherethe battery device has any other configuration such as a laminateconfiguration.

Further, in the embodiments and the examples, the case where lithium isused as an electrode reactant is described; however, any other Group 1element such as sodium (Na) or potassium (K), a Group 2 element such asmagnesium (Mg) or calcium (Ca), or any other light metal such asaluminum may be used. As the effects of the technology is supposed to beobtained without relying on the kind of the electrode reactant, similareffects are obtainable even if the kind of the electrode reactant ischanged.

In the embodiments and the examples, an appropriate range, which isderived from the results of the examples, of the content of themethylene cyclic carbonate is described; however, the description doesnot exclude the possibility that the content is out of theabove-described range. More specifically, the above-describedappropriate range is a specifically preferable range to obtain theeffects of the technology, and as long as the effects of the technologyare obtained, the content may be deviated from the above-described rangeto some extent. The same applies to the contents of other materials.

It is to be noted that the technology is allowed to have the followingconfigurations.

(1) A secondary battery including:

a cathode, an anode, and a nonaqueous electrolytic solution in a packagemember having a flat surface,

in which the nonaqueous electrolytic solution includes a methylenecyclic carbonate represented by an expression (1):

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygencontaining monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other.

(2) The secondary battery according to (1), in which

the halogen group is a fluorine group, a chlorine group, a brominegroup, or an iodine group,

the monovalent hydrocarbon group or the monovalent halogenatedhydrocarbon group is an alkyl group having 1 to 12 carbon atoms, analkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to12 carbon atoms, an aryl group having 6 to 18 carbon atoms, a cycloalkylgroup having 3 to 18 carbon atoms, or a group in which one or more ofhydrogen groups in any of the groups is substituted with a halogengroup, and

the oxygen-containing monovalent hydrocarbon group or theoxygencontaining monovalent halogenated hydrocarbon group is an alkoxygroup having 1 to 12 carbon atoms, or a group in which one or more ofhydrogen groups in the alkoxy group is substituted with a halogen group.

(3) The secondary battery according to (1) or (2), in which

the content of the methylene cyclic carbonate in the nonaqueouselectrolytic solution is within a range of approximately 0.01 wt % to 10wt % both inclusive.

(4) The secondary battery according to any one of (1) to (3), in which

the package member is a battery can or a laminate film.

(5) The secondary battery according to any one of (1) to (4), in which

the secondary battery is a lithium secondary battery.

(6) The secondary battery according to any one of (1) to (5), in which

the nonaqueous electrolytic solution includes an unsaturated cycliccarbonate represented by an expression (2), and

conditions: that A be approximately 0.01 wt % to 5 wt % both inclusive;B be equal to approximately 0.01 wt % to 5 wt % both inclusive; and thatB/A be equal to approximately 0.002 to 500 both inclusive are allsatisfied, where the content of the unsaturated cyclic carbonate in thenonaqueous electrolytic solution is A (wt %), and the content of themethylene cyclic carbonate in the nonaqueous electrolytic solution is B(wt %):

where R11 and R12 each are a hydrogen group or an alkyl group.

(7) The secondary battery according to (6), in which

the unsaturated cyclic carbonate is vinylene carbonate(1,3-dioxol-2-one) or methyl vinylene carbonate(4-methyl-1,3-dioxol-2-one).

(8) The secondary battery according to any one of (1) to (5), in which

the nonaqueous electrolytic solution includes a halogenated carbonate,

the halogenated carbonate includes one or both of a halogenated cycliccarbonate represented by an expression (4) and a halogenated chaincarbonate represented by an expression (5),

conditions: that C be equal to approximately 0.01 wt % to 30 wt % bothinclusive; that D be equal to approximately 0.01 wt % to 5 wt % bothinclusive; and that D/C be equal to approximately 1/3000 to 500 bothinclusive are all satisfied, where the content of the halogenatedcarbonate in the nonaqueous electrolytic solution is C (wt %), and thecontent of the methylene cyclic carbonate in the nonaqueous electrolyticsolution is D (wt %):

where R17 to R20 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R17 to R20 is a halogen group or a monovalenthalogenated hydrocarbon group, and

where R21 to R26 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R21 to R26 is a halogen group or a monovalenthalogenated hydrocarbon group.

(9) The secondary battery according to (8), in which

the halogenated carbonate is 4-fluoro-1,3-dioxolane-2-one.

(10) The secondary battery according to any one of (1) to (5), in which

the nonaqueous electrolytic solution includes ethylene carbonate(1,3-dioxolane-2-one) and propylene carbonate(4-methyl-1,3-dioxolane-2-one),

a mixture ratio of the ethylene carbonate and the propylene carbonate inweight ratio is within a range of approximately 75:25 to 25:75 bothinclusive, and

the content of the methylene cyclic carbonate in the nonaqueouselectrolytic solution is within a range of approximately 0.01 wt % to 10wt % both inclusive.

Moreover, the technology is allowed to have the followingconfigurations.

(11) A secondary battery including:

a cathode;

an anode; and

a nonaqueous electrolytic solution, the nonaqueous electrolytic solutionincluding a methylene cyclic carbonate represented by an expression (11)and one or more kinds selected from compounds represented by expressions(12) to (16):

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygencontaining monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other,

where R71 and R73 each are a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, an oxygen-containing monovalenthydrocarbon group, or an oxygen-containing monovalent halogenatedhydrocarbon group, R72 is a divalent hydrocarbon group, a divalenthalogenated hydrocarbon group, an oxygen-containing divalent hydrocarbongroup, or an oxygen-containing divalent halogenated hydrocarbon group,

where R74 and R76 each are a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, an oxygen-containing monovalenthydrocarbon group, or an oxygen-containing monovalent halogenatedhydrocarbon group, R75 is a divalent hydrocarbon group, a divalenthalogenated hydrocarbon group, an oxygen-containing divalent hydrocarbongroup, or an oxygen-containing divalent halogenated hydrocarbon group,and n is an integer of 1 or more,

where R77 and R79 each are a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, an oxygen-containing monovalenthydrocarbon group, or an oxygen-containing monovalent halogenatedhydrocarbon group, and R78 is a divalent hydrocarbon group, a divalenthalogenated hydrocarbon group, an oxygencontaining divalent hydrocarbongroup, an oxygen-containing divalent halogenated hydrocarbon group,

Li₂PFO₃  (15), and

LiPF₂O₂  (16)

(12) The secondary battery according to (11), in which

in R1 and R2,

the halogen group is a fluorine group, a chlorine group, a brominegroup, or an iodine group,

the monovalent hydrocarbon group or the monovalent halogenatedhydrocarbon group is an alkyl group having 1 to 12 carbon atoms, analkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to12 carbon atoms, an aryl group having 6 to 18 carbon atoms, a cycloalkylgroup having 3 to 18 carbon atoms, and a group in which one or more ofhydrogen groups in any of the groups is substituted with a halogengroup,

the oxygen-containing monovalent hydrocarbon group or theoxygencontaining monovalent halogenated hydrocarbon group is an alkoxygroup having 1 to 12 carbon atoms, or a group in which one or more ofhydrogen groups in the alkoxy group is substituted with a halogen group,

in R71 to R79,

the monovalent hydrocarbon group or the monovalent halogenatedhydrocarbon group is an alkyl group having 1 to 12 carbon atoms, analkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to12 carbon atoms, an aryl group having 6 to 18 carbon atoms, a cycloalkylgroup having 6 to 18 carbon atoms, or a group in which one or more ofhydrogen groups in any of the groups is substituted with a halogengroup,

the oxygen-containing monovalent hydrocarbon group or theoxygencontaining monovalent halogenated hydrocarbon group is an alkoxygroup having 1 to 12 carbon atoms, or a group in which one or more ofhydrogen groups in the alkoxy group is substituted with a halogen group,

the divalent hydrocarbon group or the divalent halogenated hydrogengroup is an alkylene group having 1 to 12 carbon atoms, an alkenylenegroup having 2 to 12 carbon atoms, an alkynylene group having 2 to 12carbon atoms, an arylene group having 6 to 18 carbon atoms, acycloalkylene group having 3 to 18 carbon atoms, a group including anarylene group and an alkylene group, or a group in which one or more ofhydrogen groups in any of the groups is substituted with a halogengroup, and

the oxygen-containing divalent hydrocarbon group or theoxygen-containing divalent halogenated hydrocarbon group is a groupincluding an ether bond and an alkylene group, or a group in which oneor more of hydrogen groups in the group is substituted with a halogengroup.

(13) The secondary battery according to (11) or (12), in which

the content of the methylene cyclic carbonate in the nonaqueouselectrolytic solution is within a range of approximately 0.01 wt % to 10wt % both inclusive, and the content of the compound in the nonaqueouselectrolytic solution is within a range of approximately 0.001 wt % to 2wt % both inclusive.

(14) The secondary battery according to any one of (11) to (13), inwhich

the nonaqueous electrolytic solution includes an unsaturated cycliccarbonate represented by an expression (2), and

conditions: that A be approximately 0.01 wt % to 5 wt % both inclusive;B be equal to approximately 0.01 wt % to 5 wt % both inclusive; and thatB/A be equal to approximately 0.002 to 500 both inclusive are allsatisfied, where the content of the unsaturated cyclic carbonate in thenonaqueous electrolytic solution is A (wt %), and the content of themethylene cyclic carbonate in the nonaqueous electrolytic solution is B(wt %):

where R11 and R12 each are a hydrogen group or an alkyl group.

(15) The secondary battery according to (14), in which

the unsaturated cyclic carbonate is vinylene carbonate(1,3-dioxol-2-one) or methyl vinylene carbonate(4-methyl-1,3-dioxol-2-one)

(16) The secondary battery according to any one of (11) to (13), inwhich

the nonaqueous electrolytic solution includes a halogenated carbonate,

the halogenated carbonate includes one or both of a halogenated cycliccarbonate represented by an expression (4) and a halogenated chaincarbonate represented by an expression (5),

conditions: that C be equal to approximately 0.01 wt % to 30 wt % bothinclusive; that D be equal to approximately 0.01 wt % to 5 wt % bothinclusive; and that D/C be equal to approximately 1/3000 to 500 bothinclusive are all satisfied, where the content of the halogenatedcarbonate in the nonaqueous electrolytic solution is C (wt %), and thecontent of the methylene cyclic carbonate in the nonaqueous electrolyticsolution is D (wt %):

where R17 to R20 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R17 to R20 is a halogen group or a monovalenthalogenated hydrocarbon group, and

where R21 to R26 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R21 to R26 is a halogen group or a monovalenthalogenated hydrocarbon group.

(17) The secondary battery according to (16), in which

the halogenated carbonate is 4-fluoro-1,3-dioxolane-2-one.

(18) The secondary battery according to any one of (11) to (13), inwhich

the nonaqueous electrolytic solution includes ethylene carbonate(1,3-dioxolane-2-one) and propylene carbonate(4-methyl-1,3-dioxolane-2-one),

a mixture ratio of the ethylene carbonate and the propylene carbonate inweight ratio is within a range of approximately 75:25 to 25:75 bothinclusive, and

the content of the methylene cyclic carbonate in the nonaqueouselectrolytic solution is within a range of approximately 0.01 wt % to 10wt % both inclusive.

Further, the technology is allowed to have the following configurations.

(19) A secondary battery including:

a cathode;

an anode; and

a nonaqueous electrolytic solution, the nonaqueous electrolytic solutionincluding a methylene cyclic carbonate represented by an expression(17), and one or both of halogenated carbonates represented byexpressions (18) and (19):

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygencontaining monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other,

where R17 to R20 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R17 to R20 is a halogen group or a monovalenthalogenated hydrocarbon group, and

where R21 to R26 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R21 to R26 is a halogen group or a monovalenthalogenated hydrocarbon group.

(20) The secondary battery according to (19), in which

in R1 and R2,

the halogen group is a fluorine group, a chlorine group, a brominegroup, or an iodine group,

the monovalent hydrocarbon group or the monovalent halogenatedhydrocarbon group is an alkyl group having 1 to 12 carbon atoms, analkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to12 carbon atoms, an aryl group having 6 to 18 carbon atoms, a cycloalkylgroup having 3 to 18 carbon atoms, and a group in which one or more ofhydrogen groups in any of the groups is substituted with a halogengroup,

the oxygen-containing monovalent hydrocarbon group or theoxygencontaining monovalent halogenated hydrocarbon group is an alkoxygroup having 1 to

12 carbon atoms, or a group in which one or more of hydrogen groups inthe alkoxy group is substituted with a halogen group,

in R17 to R26,

the halogen group is a fluorine group, a chlorine group, a brominegroup, or an iodine group, and the monovalent hydrocarbon group or themonovalent halogenated hydrocarbon group is an alkyl group having 1 to12 carbon atoms, or a group in which one or more of hydrogen groups inthe alkyl group is substituted with a halogen group.

(21) The secondary battery according to (19) or (20), in which

the content of the methylene cyclic carbonate in the nonaqueouselectrolytic solution is within a range of approximately 0.01 wt % to 10wt % both inclusive, and the content of the halogenated carbonate in thenonaqueous electrolytic solution is within a range of approximately 0.1wt % to 20 wt % both inclusive.

(22) The secondary battery according to any one of (19) to (21), inwhich

the nonaqueous electrolytic solution includes an unsaturated cycliccarbonate represented by an expression (2), and

conditions: that A be approximately 0.01 wt % to 5 wt % both inclusive;B be equal to approximately 0.01 wt % to 5 wt % both inclusive; and thatB/A be equal to approximately 0.002 to 500 both inclusive are allsatisfied, where the content of the unsaturated cyclic carbonate in thenonaqueous electrolytic solution is A (wt %), and the content of themethylene cyclic carbonate in the nonaqueous electrolytic solution is B(wt %):

where R11 and R12 each are a hydrogen group or an alkyl group.

(23) The secondary battery according to (22), in which

the unsaturated cyclic carbonate is vinylene carbonate(1,3-dioxol-2-one) or methyl vinylene carbonate(4-methyl-1,3-dioxol-2-one).

(24) The secondary battery according to any one of (19) to (22), inwhich

conditions: that C be equal to approximately 0.01 wt % to 30 wt % bothinclusive; that D be equal to approximately 0.01 wt % to 5 wt % bothinclusive; and that D/C be equal to approximately 1/3000 to 500 bothinclusive are all satisfied, where the content of the halogenatedcarbonate in the nonaqueous electrolytic solution is C (wt %), and thecontent of the methylene cyclic carbonate in the nonaqueous electrolyticsolution is D (wt %).

(25) The secondary battery according to (24), in which

the halogenated carbonate is 4-fluoro-1,3-dioxolane-2-one.

(26) The secondary battery according to any one of (19) to (21), inwhich

the nonaqueous electrolytic solution includes ethylene carbonate(1,3-dioxolane-2-one) and propylene carbonate(4-methyl-1,3-dioxolane-2-one),

a mixture ratio of the ethylene carbonate and the propylene carbonate inweight ratio is within a range of approximately 75:25 to 25:75 bothinclusive, and

the content of the methylene cyclic carbonate in the nonaqueouselectrolytic solution is within a range of approximately 0.01 wt % to 10wt % both inclusive.

Moreover, the technology is allowed to have the followingconfigurations.

(27) A secondary battery including:

a cathode;

an anode; and

a nonaqueous electrolytic solution, the nonaqueous electrolytic solutionincluding one or more kinds of methylene cyclic carbonates representedby expressions (20) to (22):

where R81 is a monovalent chain unsaturated hydrocarbon group, amonovalent chain halogenated unsaturated hydrocarbon group, a halogengroup, or a monovalent chain halogenated saturated hydrocarbon group,

where R82 and R83 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, a monovalent halogenated hydrocarbongroup, an oxygen-containing monovalent hydrocarbon group, or anoxygen-containing monovalent halogenated hydrocarbon group, and one orboth of R82 and R83 are a monovalent cyclic hydrocarbon group or amonovalent halogenated cyclic hydrocarbon group, and

where R84 is a divalent hydrocarbon group or a divalent halogenatedhydrocarbon group.

(28) The secondary battery according to (27), in which

in R81,

the monovalent chain unsaturated hydrocarbon group or the monovalentchain halogenated unsaturated hydrocarbon group is an alkenyl grouphaving 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbonatoms, an aryl group having 6 to 18 carbon atoms, a group in which anaryl group having 6 to 18 carbon atoms and an alkylene group having 1 to12 carbon atoms are bonded to each other, a group in which a hydrogengroup in the middle of an alkyl group having 1 to 12 carbon atoms issubstituted with an aryl group having 6 to 18 carbon atoms, or a groupin which one or more of hydrogen groups in any of the groups issubstituted with a halogen group,

the halogen group is a fluorine group, a chlorine group, a brominegroup, or an iodine group,

the monovalent chain halogenated saturated hydrocarbon group is an alkylgroup having 1 to 12 carbon atoms, an alkenyl group having 2 to 12carbon atoms, or a group in which one or more of hydrogen groups in analkynyl group having 2 to 12 carbon atoms is substituted with a halogengroup,

in R82 and R83,

the halogen group is a fluorine group, a chlorine group, a brominegroup, or an iodine group,

the monovalent hydrocarbon group or the monovalent halogenatedhydrocarbon group is an alkyl group having 1 to 12 carbon atoms, analkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to12 carbon atoms, an aryl group having 6 to 18 carbon atoms, a cycloalkylgroup having 3 to 18 carbon atoms, or a group in which one or more ofhydrogen groups in any of the groups is substituted with a halogengroup,

the oxygen-containing monovalent hydrocarbon group or theoxygencontaining monovalent halogenated hydrocarbon group is an alkoxygroup having 1 to 12 carbon atoms, or a group in which one or more ofhydrogen groups in the alkoxy group is substituted with a halogen group,

the monovalent cyclic hydrocarbon group or the monovalent halogenatedcyclic hydrocarbon group is an aryl group having 6 to 18 carbon atoms, agroup in which an aryl group having 6 to 18 carbon atoms and an alkylenegroup having 1 to 12 carbon atoms are bonded to each other, a cycloalkylgroup having 6 to 18 carbon atoms, a group in which a cycloalkyl grouphaving 6 to 18 carbon atoms and an alkylene group having 1 to 12 carbonatoms are bonded to each other, or a group in which one or more ofhydrogen groups in any of the groups is substituted with a halogengroup, and

in R84,

the divalent hydrocarbon group or the divalent halogenated hydrogengroup is an alkylene group having 1 to 12 carbon atoms, or a group inwhich one or more of hydrogen groups in the alkylene group issubstituted with a halogen group.

(29) The secondary battery according to (27) or (28), in which

the content of the methylene cyclic carbonate in the nonaqueouselectrolytic solution is within a range of approximately 0.01 wt % to 10wt % both inclusive.

(30) The secondary battery according to any one of (27) to (29), inwhich

the nonaqueous electrolytic solution includes an unsaturated cycliccarbonate represented by an expression (2), and

conditions: that A be approximately 0.01 wt % to 5 wt % both inclusive;B be equal to approximately 0.01 wt % to 5 wt % both inclusive; and thatB/A be equal to approximately 0.002 to 500 both inclusive are allsatisfied, where the content of the unsaturated cyclic carbonate in thenonaqueous electrolytic solution is A (wt %), and the content of themethylene cyclic carbonate in the nonaqueous electrolytic solution is B(wt %):

where R11 and R12 each are a hydrogen group or an alkyl group.

(31) The secondary battery according to (30), in which

the unsaturated cyclic carbonate is vinylene carbonate(1,3-dioxol-2-one) or methyl vinylene carbonate(4-methyl-1,3-dioxol-2-one).

(32) The secondary battery according to any one of (27) to (29), inwhich

the nonaqueous electrolytic solution includes a halogenated carbonate,

the halogenated carbonate includes one or both of a halogenated cycliccarbonate represented by an expression (4) and a halogenated chaincarbonate represented by an expression (5),

conditions: that C be equal to approximately 0.01 wt % to 30 wt % bothinclusive; that D be equal to approximately 0.01 wt % to 5 wt % bothinclusive; and that D/C be equal to approximately 1/3000 to 500 bothinclusive are all satisfied, where the content of the halogenatedcarbonate in the nonaqueous electrolytic solution is C (wt %), and thecontent of the methylene cyclic carbonate in the nonaqueous electrolyticsolution is D (wt %):

where R17 to R20 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R17 to R20 is a halogen group or a monovalenthalogenated hydrocarbon group, and

where R21 to R26 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R21 to R26 is a halogen group or a monovalenthalogenated hydrocarbon group.

(33) The secondary battery according to (32), in which

the halogenated carbonate is 4-fluoro-1,3-dioxolane-2-one.

(34) The secondary battery according to any one of (27) to (29), inwhich

the nonaqueous electrolytic solution includes ethylene carbonate(1,3-dioxolane-2-one) and propylene carbonate(4-methyl-1,3-dioxolane-2-one),

a mixture ratio of the ethylene carbonate and the propylene carbonate inweight ratio is within a range of approximately 75:25 to 25:75 bothinclusive, and

the content of the methylene cyclic carbonate in the nonaqueouselectrolytic solution is within a range of approximately 0.01 wt % to 10wt % both inclusive.

Further, the technology is allowed to have the following configurations.

(35) A secondary battery including:

a cathode, an anode, and a nonaqueous electrolytic solution, thenonaqueous electrolytic solution including a methylene cyclic carbonaterepresented by an expression (23) and an unsaturated cyclic carbonaterepresented by an expression (24),

in which conditions: that A be approximately 0.01 wt % to 5 wt % bothinclusive; B be equal to approximately 0.01 wt % to 5 wt % bothinclusive; and that B/A be equal to approximately 0.002 to 500 bothinclusive are all satisfied, where the content of the unsaturated cycliccarbonate in the nonaqueous electrolytic solution is A (wt %), and thecontent of the methylene cyclic carbonate in the nonaqueous electrolyticsolution is B (wt %):

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygencontaining monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other, and

where R11 and R12 each are a hydrogen group or an alkyl group.

(36) The secondary battery according to (35), in which

the halogen group is a fluorine group, a chlorine group, a brominegroup, or an iodine group,

the monovalent hydrocarbon group or the monovalent halogenatedhydrocarbon group is an alkyl group having 1 to 12 carbon atoms, analkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to12 carbon atoms, an aryl group having 6 to 18 carbon atoms, a cycloalkylgroup having 3 to 18 carbon atoms, or a group in which one or more ofhydrogen groups in any of the groups is substituted with a halogengroup,

and the oxygen-containing monovalent hydrocarbon group or theoxygencontaining monovalent halogenated hydrocarbon group is an alkoxygroup having 1 to 12 carbon atoms, or a group in which one or more ofhydrogen groups in the alkoxy group is substituted with a halogen group.

(37) The secondary battery according to (35) or (36), in which

the unsaturated cyclic carbonate is vinylene carbonate(1,3-dioxol-2-one) or methyl vinylene carbonate(4-methyl-1,3-dioxol-2-one).

(38) The secondary battery according to any one of (35) to (37), inwhich

the nonaqueous electrolytic solution includes a halogenated carbonate,the halogenated carbonate includes one or both of a halogenated cycliccarbonate represented by an expression (4) and a halogenated chaincarbonate represented by an expression (5),

conditions: that C be equal to approximately 0.01 wt % to 30 wt % bothinclusive; that D be equal to approximately 0.01 wt % to 5 wt % bothinclusive; and that D/C be equal to approximately 1/3000 to 500 bothinclusive are all satisfied, where the content of the halogenatedcarbonate in the nonaqueous electrolytic solution is C (wt %), and thecontent of the methylene cyclic carbonate in the nonaqueous electrolyticsolution is D (wt %):

where R17 to R20 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R17 to R20 is a halogen group or a monovalenthalogenated hydrocarbon group, and

where R21 to R26 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R21 to R26 is a halogen group or a monovalenthalogenated hydrocarbon group.

(39) The secondary battery according to (38), in which

the halogenated carbonate is 4-fluoro-1,3-dioxolane-2-one.

(40) The secondary battery according to any one of (35) to (37), inwhich

the nonaqueous electrolytic solution includes ethylene carbonate(1,3-dioxolane-2-one) and propylene carbonate(4-methyl-1,3-dioxolane-2-one),

a mixture ratio of the ethylene carbonate and the propylene carbonate inweight ratio is within a range of approximately 75:25 to 25:75 bothinclusive, and

the content of the methylene cyclic carbonate in the nonaqueouselectrolytic solution is within a range of approximately 0.01 wt % to 10wt % both inclusive.

Moreover, the technology is allowed to have the followingconfigurations.

(41) A nonaqueous electrolytic solution including:

a methylene cyclic carbonate represented by an expression (11); and

one or more kinds selected from compounds represented by expressions(12) to (16):

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygencontaining monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other,

where R71 and R73 each are a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, an oxygen-containing monovalenthydrocarbon group, or an oxygen-containing monovalent halogenatedhydrocarbon group, R72 is a divalent hydrocarbon group, a divalenthalogenated hydrocarbon group, an oxygen-containing divalent hydrocarbongroup, or an oxygen-containing divalent halogenated hydrocarbon group,

where R74 and R76 each are a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, an oxygen-containing monovalenthydrocarbon group, or an oxygen-containing monovalent halogenatedhydrocarbon group, R75 is a divalent hydrocarbon group, a divalenthalogenated hydrocarbon group, an oxygen-containing divalent hydrocarbongroup, or an oxygen-containing divalent halogenated hydrocarbon group,and n is an integer of 1 or more,

where R77 and R79 each are a monovalent hydrocarbon group, a monovalenthalogenated hydrocarbon group, an oxygen-containing monovalenthydrocarbon group, or an oxygen-containing monovalent halogenatedhydrocarbon group, and R78 is a divalent hydrocarbon group, a divalenthalogenated hydrocarbon group, an oxygencontaining divalent hydrocarbongroup, or an oxygen-containing divalent halogenated hydrocarbon group,

Li₂PFO₃  (15), and

LiPF₂O₂  (16)

(42) A nonaqueous electrolytic solution including:

a methylene cyclic carbonate represented by an expression (17); and

one or both of halogenated carbonates represented by expressions (18)and (19):

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygencontaining monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other,

where R17 to R20 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R17 to R20 is a halogen group or a monovalenthalogenated hydrocarbon group, and

where R21 to R26 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R21 to R26 is a halogen group or a monovalenthalogenated hydrocarbon group.

(43) A nonaqueous electrolytic solution including one or more kindsselected from methylene cyclic carbonates represented by expressions(20) to (22):

where R81 is a monovalent chain unsaturated hydrocarbon group, amonovalent chain halogenated unsaturated hydrocarbon group, a halogengroup, or a monovalent chain halogenated saturated hydrocarbon group,

where R82 and R83 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, a monovalent halogenated hydrocarbongroup, an oxygen-containing monovalent hydrocarbon group, or anoxygen-containing monovalent halogenated hydrocarbon group, and one orboth of R82 and R83 are a monovalent cyclic hydrocarbon group or amonovalent halogenated cyclic hydrocarbon group, and

where R84 is a divalent hydrocarbon group or a divalent halogenatedhydrocarbon group.

(44) A nonaqueous electrolytic solution including:

a methylene cyclic carbonate represented by an expression (23) and anunsaturated cyclic carbonate represented by an expression (24),

in which conditions: that A be approximately 0.01 wt % to 5 wt % bothinclusive; B be equal to approximately 0.01 wt % to 5 wt % bothinclusive; and that B/A be equal to approximately 0.002 to 500 bothinclusive are all satisfied, where the content of the unsaturated cycliccarbonate in the nonaqueous electrolytic solution is A (wt %), and thecontent of the methylene cyclic carbonate in the nonaqueous electrolyticsolution is B (wt %):

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygencontaining monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other, and

where R11 and R12 each are a hydrogen group or an alkyl group.

Further, the technology is allowed to have the following configurations.

(45) A battery pack including:

the secondary battery according to any one of (1) to (40);

a control section controlling a usage state of the secondary battery;and

a switch section switching the usage state of the secondary batteryaccording to an instruction from the control section.

(46) An electric vehicle including:

the secondary battery according to any one of (1) to (40);

a conversion section converting power supplied from the secondarybattery into driving force;

a drive section driven by the driving force; and

a control section controlling a usage state of the secondary battery.

(47) An energy storage system including:

the secondary battery according to any one of (1) to (40);

one or two or more electrical units receiving power from the secondarybattery; and

a control section controlling power supply from the secondary battery tothe electrical unit.

(48) An electric power tool including:

the secondary battery according to any one of (1) to (40); and

a movable section receiving power from the secondary battery.

(49) An electronic unit including the secondary battery according to anyone of (1) to (40) as a power supply.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

1. A secondary battery comprising: a cathode, an anode, and a nonaqueouselectrolytic solution in a package member having a flat surface, whereinthe nonaqueous electrolytic solution includes a methylene cycliccarbonate represented by an expression (1):

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygen-containing monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other.
 2. The secondary battery according to claim 1, wherein thehalogen group is a fluorine group, a chlorine group, a bromine group, oran iodine group, the monovalent hydrocarbon group or the monovalenthalogenated hydrocarbon group is an alkyl group having 1 to 12 carbonatoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl grouphaving 2 to 12 carbon atoms, an aryl group having 6 to 18 carbon atoms,a cycloalkyl group having 3 to 18 carbon atoms, or a group in which oneor more of hydrogen groups in any of the groups is substituted with ahalogen group, and the oxygen-containing monovalent hydrocarbon group orthe oxygen-containing monovalent halogenated hydrocarbon group is analkoxy group having 1 to 12 carbon atoms, or a group in which one ormore of hydrogen groups in the alkoxy group is substituted with ahalogen group.
 3. The secondary battery according to claim 1, whereinthe content of the methylene cyclic carbonate in the nonaqueouselectrolytic solution is within a range of approximately 0.01 wt % to 10wt % both inclusive.
 4. The secondary battery according to claim 1,wherein the package member is a battery can or a laminate film.
 5. Thesecondary battery according to claim 1, wherein the secondary battery isa lithium secondary battery.
 6. The secondary battery according to claim1, wherein the nonaqueous electrolytic solution includes an unsaturatedcyclic carbonate represented by an expression (2), and conditions: thatA be approximately 0.01 wt % to 5 wt % both inclusive; B be equal toapproximately 0.01 wt % to 5 wt % both inclusive; and that B/A be equalto approximately 0.002 to 500 both inclusive are all satisfied, wherethe content of the unsaturated cyclic carbonate in the nonaqueouselectrolytic solution is A (wt %), and the content of the methylenecyclic carbonate in the nonaqueous electrolytic solution is B (wt %):

where R11 and R12 each are a hydrogen group or an alkyl group.
 7. Thesecondary battery according to claim 6, wherein the unsaturated cycliccarbonate is vinylene carbonate (1,3-dioxol-2-one) or methyl vinylenecarbonate (4-methyl-1,3-dioxol-2-one)
 8. The secondary battery accordingto claim 1, wherein the nonaqueous electrolytic solution includes ahalogenated carbonate, the halogenated carbonate includes one or both ofa halogenated cyclic carbonate represented by an expression (4) and ahalogenated chain carbonate represented by an expression (5),conditions: that C be equal to approximately 0.01 wt % to 30 wt % bothinclusive; that D be equal to approximately 0.01 wt % to 5 wt % bothinclusive; and that D/C be equal to approximately 1/3000 to 500 bothinclusive are all satisfied, where the content of the halogenatedcarbonate in the nonaqueous electrolytic solution is C (wt %), and thecontent of the methylene cyclic carbonate in the nonaqueous electrolyticsolution is D (wt %):

where R17 to R20 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R17 to R20 is a halogen group or a monovalenthalogenated hydrocarbon group, and

where R21 to R26 each are a hydrogen group, a halogen group, amonovalent hydrocarbon group, or a monovalent halogenated hydrocarbongroup, and one or more of R21 to R26 is a halogen group or a monovalenthalogenated hydrocarbon group.
 9. The secondary battery according toclaim 8, wherein the halogenated carbonate is4-fluoro-1,3-dioxolane-2-one.
 10. The secondary battery according toclaim 1, wherein the nonaqueous electrolytic solution includes ethylenecarbonate (1,3-dioxolane-2-one) and propylene carbonate(4-methyl-1,3-dioxolane-2-one), a mixture ratio of the ethylenecarbonate and the propylene carbonate in weight ratio is within a rangeof approximately 75:25 to 25:75 both inclusive, and the content of themethylene cyclic carbonate in the nonaqueous electrolytic solution iswithin a range of approximately 0.01 wt % to 10 wt % both inclusive. 11.A battery pack comprising: a secondary battery; a control sectioncontrolling a usage state of the secondary battery; and a switch sectionswitching the usage state of the secondary battery according to aninstruction from the control section, wherein the secondary batteryincludes a cathode, an anode, and a nonaqueous electrolytic solution ina package member having a flat surface, and the nonaqueous electrolyticsolution includes a methylene cyclic carbonate represented by anexpression (1):

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygen-containing monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other.
 12. An electric vehicle comprising: a secondary battery; aconversion section converting power supplied from the secondary batteryinto driving force; a drive section driven by the driving force; and acontrol section controlling a usage state of the secondary battery,wherein the secondary battery includes a cathode, an anode, and anonaqueous electrolytic solution in a package member having a flatsurface, and the nonaqueous electrolytic solution includes a methylenecyclic carbonate represented by an expression (1):

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygen-containing monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other.
 13. An energy storage system comprising: a secondarybattery; one or two or more electrical units receiving power from thesecondary battery; and a control section controlling power supply fromthe secondary battery to the electrical unit, wherein the secondarybattery includes a cathode, an anode, and a nonaqueous electrolyticsolution in a package member having a flat surface, and the nonaqueouselectrolytic solution includes a methylene cyclic carbonate representedby an expression (1):

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygen-containing monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other.
 14. An electric power tool comprising: a secondary battery;and a movable section receiving power from the secondary battery,wherein the secondary battery includes a cathode, an anode, and anonaqueous electrolytic solution in a package member having a flatsurface, and the nonaqueous electrolytic solution includes a methylenecyclic carbonate represented by an expression (1):

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygen-containing monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other.
 15. An electronic unit comprising a secondary battery as apower supply, the secondary battery including a cathode, an anode, and anonaqueous electrolytic solution in a package member having a flatsurface, wherein the nonaqueous electrolytic solution includes amethylene cyclic carbonate represented by an expression (1):

where R1 and R2 each are a hydrogen group, a halogen group, a monovalenthydrocarbon group, a monovalent halogenated hydrocarbon group, anoxygen-containing monovalent hydrocarbon group, or an oxygen-containingmonovalent halogenated hydrocarbon group, and R1 and R2 may be bonded toeach other.